diff --git a/core/.stylelintrc.json b/core/.stylelintrc.json
index 832748d391..0155085290 100644
--- a/core/.stylelintrc.json
+++ b/core/.stylelintrc.json
@@ -6,8 +6,6 @@
   "rules": {
     "at-rule-empty-line-before": null,
     "block-no-empty": null,
-    "color-hex-case": null,
-    "color-hex-length": null,
     "comment-empty-line-before": null,
     "declaration-block-no-duplicate-properties": null,
     "declaration-block-no-redundant-longhand-properties": null,
diff --git a/core/modules/block_place/css/block-place.css b/core/modules/block_place/css/block-place.css
index aa3eccb5ad..72b0f40c87 100644
--- a/core/modules/block_place/css/block-place.css
+++ b/core/modules/block_place/css/block-place.css
@@ -14,8 +14,8 @@
 
 .block-place-region a.button {
   position: relative;
-  background: url(../../../misc/icons/bebebe/plus.svg) #ffffff center center / 16px 16px no-repeat;
-  border: 1px solid #cccccc;
+  background: url(../../../misc/icons/bebebe/plus.svg) #fff center center / 16px 16px no-repeat;
+  border: 1px solid #ccc;
   box-sizing: border-box;
   font-size: 1rem;
   padding: 0;
diff --git a/core/modules/ckeditor/css/ckeditor.css b/core/modules/ckeditor/css/ckeditor.css
index b4b1e16cec..bc2c43a6be 100644
--- a/core/modules/ckeditor/css/ckeditor.css
+++ b/core/modules/ckeditor/css/ckeditor.css
@@ -7,7 +7,7 @@
 
 .ckeditor-dialog-loading-link {
   border-radius: 0 0 5px 5px;
-  border: 1px solid #B6B6B6;
+  border: 1px solid #b6b6b6;
   border-top: none;
   background: white;
   padding: 3px 10px;
diff --git a/core/modules/color/tests/modules/color_test/themes/color_test_theme/css/colors.css b/core/modules/color/tests/modules/color_test/themes/color_test_theme/css/colors.css
index 07a4193b8a..fa6836bd64 100644
--- a/core/modules/color/tests/modules/color_test/themes/color_test_theme/css/colors.css
+++ b/core/modules/color/tests/modules/color_test/themes/color_test_theme/css/colors.css
@@ -1,7 +1,7 @@
 html {
-  color: #0000ff;
+  color: #00f;
 }
 
 body {
-  color: #ff0000;
+  color: #f00;
 }
diff --git a/core/modules/shortcut/css/shortcut.theme.css b/core/modules/shortcut/css/shortcut.theme.css
index 73d58c6d46..3fe631c676 100644
--- a/core/modules/shortcut/css/shortcut.theme.css
+++ b/core/modules/shortcut/css/shortcut.theme.css
@@ -32,11 +32,11 @@
   margin-right: 0.3em;
 }
 .shortcut-action__message {
-  background: #000000;
+  background: #000;
   background: rgba(0, 0, 0, 0.5);
   border-radius: 5px;
   padding: 0 5px;
-  color: #ffffff;
+  color: #fff;
   display: inline-block;
   margin-left: 0.3em; /* LTR */
   opacity: 0;
diff --git a/core/modules/system/css/system.admin.css b/core/modules/system/css/system.admin.css
index be739ac11d..e42cee09a1 100644
--- a/core/modules/system/css/system.admin.css
+++ b/core/modules/system/css/system.admin.css
@@ -117,7 +117,7 @@ small .admin-link:after {
   text-transform: none;
 }
 .system-modules td details a {
-  color: #5C5C5B;
+  color: #5c5c5b;
   border: 0px;
 }
 .system-modules td details {
diff --git a/core/modules/toolbar/css/toolbar.menu.css b/core/modules/toolbar/css/toolbar.menu.css
index 099fb08496..479c78915f 100644
--- a/core/modules/toolbar/css/toolbar.menu.css
+++ b/core/modules/toolbar/css/toolbar.menu.css
@@ -46,38 +46,38 @@
  */
 .toolbar .level-2 > ul {
   background-color: #fafafa;
-  border-bottom-color: #cccccc;
+  border-bottom-color: #ccc;
   border-top-color: #e5e5e5;
 }
 .toolbar .level-3 > ul {
   background-color: #f5f5f5;
   border-bottom-color: #c5c5c5;
-  border-top-color: #dddddd;
+  border-top-color: #ddd;
 }
 .toolbar .level-4 > ul {
-  background-color: #eeeeee;
-  border-bottom-color: #bbbbbb;
+  background-color: #eee;
+  border-bottom-color: #bbb;
   border-top-color: #d5d5d5;
 }
 .toolbar .level-5 > ul {
   background-color: #e5e5e5;
   border-bottom-color: #b5b5b5;
-  border-top-color: #cccccc;
+  border-top-color: #ccc;
 }
 .toolbar .level-6 > ul {
-  background-color: #eeeeee;
-  border-bottom-color: #aaaaaa;
+  background-color: #eee;
+  border-bottom-color: #aaa;
   border-top-color: #c5c5c5;
 }
 .toolbar .level-7 > ul {
   background-color: #fafafa;
   border-bottom-color: #b5b5b5;
-  border-top-color: #cccccc;
+  border-top-color: #ccc;
 }
 .toolbar .level-8 > ul {
-  background-color: #dddddd;
-  border-bottom-color: #cccccc;
-  border-top-color: #dddddd;
+  background-color: #ddd;
+  border-bottom-color: #ccc;
+  border-top-color: #ddd;
 }
 
 /**
diff --git a/core/modules/toolbar/css/toolbar.theme.css b/core/modules/toolbar/css/toolbar.theme.css
index 0b3afc9876..7baf6963be 100644
--- a/core/modules/toolbar/css/toolbar.theme.css
+++ b/core/modules/toolbar/css/toolbar.theme.css
@@ -31,13 +31,13 @@
 .toolbar .toolbar-bar {
   background-color: #0f0f0f;
   box-shadow: -1px 0 3px 1px rgba(0, 0, 0, 0.3333); /* LTR */
-  color: #dddddd;
+  color: #ddd;
 }
 [dir="rtl"] .toolbar .toolbar-bar {
   box-shadow: 1px 0 3px 1px rgba(0, 0, 0, 0.3333);
 }
 .toolbar .toolbar-bar .toolbar-item {
-  color: #ffffff;
+  color: #fff;
 }
 .toolbar .toolbar-bar .toolbar-tab > .toolbar-item {
   font-weight: bold;
@@ -56,7 +56,7 @@
  * Toolbar tray.
  */
 .toolbar .toolbar-tray {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 .toolbar .toolbar-tray-horizontal > .toolbar-lining {
   padding-right: 5em; /* LTR */
@@ -67,16 +67,16 @@
 }
 .toolbar .toolbar-tray-vertical {
   background-color: #f5f5f5;
-  border-right: 1px solid #aaaaaa; /* LTR */
+  border-right: 1px solid #aaa; /* LTR */
   box-shadow: -1px 0 5px 2px rgba(0, 0, 0, 0.3333); /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-vertical {
-  border-left: 1px solid #aaaaaa;
+  border-left: 1px solid #aaa;
   border-right: 0 none;
   box-shadow: 1px 0 5px 2px rgba(0, 0, 0, 0.3333);
 }
 .toolbar .toolbar-tray-horizontal {
-  border-bottom: 1px solid #aaaaaa;
+  border-bottom: 1px solid #aaa;
   box-shadow: -2px 1px 3px 1px rgba(0, 0, 0, 0.3333); /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal {
@@ -99,33 +99,33 @@
   text-decoration: underline;
 }
 .toolbar .toolbar-menu {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 .toolbar .toolbar-tray-horizontal .menu-item + .menu-item {
-  border-left: 1px solid #dddddd; /* LTR */
+  border-left: 1px solid #ddd; /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal .menu-item + .menu-item {
   border-left: 0 none;
-  border-right: 1px solid #dddddd;
+  border-right: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-horizontal .menu-item:last-child {
-  border-right: 1px solid #dddddd; /* LTR */
+  border-right: 1px solid #ddd; /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal .menu-item:last-child {
-  border-left: 1px solid #dddddd;
+  border-left: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item + .menu-item {
-  border-top: 1px solid #dddddd;
+  border-top: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item:last-child {
-  border-bottom: 1px solid #dddddd;
+  border-bottom: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item .menu-item {
   border: 0 none;
 }
 .toolbar .toolbar-tray-vertical .toolbar-menu ul ul {
-  border-bottom: 1px solid #dddddd;
-  border-top: 1px solid #dddddd;
+  border-bottom: 1px solid #ddd;
+  border-top: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item:last-child > ul {
   border-bottom: 0;
diff --git a/core/modules/views_ui/css/views_ui.admin.theme.css b/core/modules/views_ui/css/views_ui.admin.theme.css
index 30616f05cc..3029249668 100644
--- a/core/modules/views_ui/css/views_ui.admin.theme.css
+++ b/core/modules/views_ui/css/views_ui.admin.theme.css
@@ -623,10 +623,10 @@ td.group-title {
   border: none;
 }
 .views-ui-dialog .views-offset-top {
-  border-bottom: 1px solid #CCC;
+  border-bottom: 1px solid #ccc;
 }
 .views-ui-dialog .views-offset-bottom {
-  border-top: 1px solid #CCC;
+  border-top: 1px solid #ccc;
 }
 .views-ui-dialog .views-override > * {
   margin: 0;
diff --git a/core/themes/bartik/css/colors.css b/core/themes/bartik/css/colors.css
index 41dc0546cb..6d71a9e3d0 100644
--- a/core/themes/bartik/css/colors.css
+++ b/core/themes/bartik/css/colors.css
@@ -8,14 +8,14 @@ body {
 #main-wrapper,
 .region-primary-menu .menu-item a.is-active,
 .region-primary-menu .menu-item--active-trail a {
-  background: #ffffff;
+  background: #fff;
 }
 .tabs ul.primary li a.is-active {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 .tabs ul.primary li.is-active a {
-  background-color: #ffffff;
-  border-bottom-color: #ffffff;
+  background-color: #fff;
+  border-bottom-color: #fff;
 }
 #header {
   background-color: #1d84c3;
diff --git a/core/themes/bartik/css/components/captions.css b/core/themes/bartik/css/components/captions.css
index cd248094f7..1564e8be02 100644
--- a/core/themes/bartik/css/components/captions.css
+++ b/core/themes/bartik/css/components/captions.css
@@ -3,12 +3,12 @@
   margin-bottom: 1.2em;
 }
 .caption > * {
-  background: #F3F3F3;
+  background: #f3f3f3;
   padding: 0.5ex;
-  border: 1px solid #CCC;
+  border: 1px solid #ccc;
 }
 .caption > figcaption {
-  border: 1px solid #CCC;
+  border: 1px solid #ccc;
   border-top: none;
   padding-top: 0.5ex;
   font-size: small;
diff --git a/core/themes/bartik/css/components/demo-block.css b/core/themes/bartik/css/components/demo-block.css
index 44a801f17b..07da3e6435 100644
--- a/core/themes/bartik/css/components/demo-block.css
+++ b/core/themes/bartik/css/components/demo-block.css
@@ -4,7 +4,7 @@
  */
 
 .demo-block {
-  background: #ffff66;
+  background: #ff6;
   border: 1px dotted #9f9e00;
   color: #000;
   font: 90% "Lucida Grande", "Lucida Sans Unicode", sans-serif;
diff --git a/core/themes/bartik/css/components/tabs.css b/core/themes/bartik/css/components/tabs.css
index 6f232fee48..466a1952b8 100644
--- a/core/themes/bartik/css/components/tabs.css
+++ b/core/themes/bartik/css/components/tabs.css
@@ -21,9 +21,10 @@ div.tabs {
   text-shadow: 0 1px 0 #fff;
 }
 .tabs ul.primary li.is-active a {
-  background-color: #ffffff;
+  background-color: #fff;
   border: 1px solid #bbb;
 }
+
 @media screen and (max-width: 37.5em) { /* 600px */
   .tabs ul.primary {
     border-bottom: 1px solid #bbb;
diff --git a/core/themes/bartik/css/components/views.css b/core/themes/bartik/css/components/views.css
index 61712577e8..1e45f57953 100644
--- a/core/themes/bartik/css/components/views.css
+++ b/core/themes/bartik/css/components/views.css
@@ -9,7 +9,7 @@
 }
 .views-displays .tabs .open > a:hover,
 .views-displays .tabs .open > a:focus {
-  color: #0071B3;
+  color: #0071b3;
 }
 .views-displays .secondary .form-submit {
   font-size: 0.846em;
@@ -22,14 +22,14 @@
 
 /* Contextual filter options styles */
 .views-filterable-options .filterable-option:nth-of-type(even) .form-type-checkbox {
-  background-color: #F9F9F9;
+  background-color: #f9f9f9;
 }
 
 /* Views action dropbutton styles */
 .views-ui-display-tab-actions .dropbutton .form-submit {
-  color: #0071B3;
+  color: #0071b3;
 }
 .views-ui-display-tab-actions .dropbutton .form-submit:hover,
 .views-ui-display-tab-actions .dropbutton .form-submit:focus {
-  color: #018FE2;
+  color: #018fe2;
 }
diff --git a/core/themes/classy/css/components/dropbutton.css b/core/themes/classy/css/components/dropbutton.css
index cf8c40a238..45e457b8f5 100644
--- a/core/themes/classy/css/components/dropbutton.css
+++ b/core/themes/classy/css/components/dropbutton.css
@@ -5,7 +5,7 @@
 
 .js .dropbutton-widget {
   background-color: white;
-  border: 1px solid #cccccc;
+  border: 1px solid #ccc;
 }
 .js .dropbutton-widget:hover {
   border-color: #b8b8b8;
diff --git a/core/themes/seven/css/base/elements.css b/core/themes/seven/css/base/elements.css
index 6644ceae6d..4dbd051951 100644
--- a/core/themes/seven/css/base/elements.css
+++ b/core/themes/seven/css/base/elements.css
@@ -23,7 +23,7 @@ hr {
   padding: 0;
   border: none;
   height: 1px;
-  background: #cccccc;
+  background: #ccc;
 }
 summary,
 .fieldgroup:not(.form-composite) > legend {
diff --git a/core/themes/seven/css/components/buttons.css b/core/themes/seven/css/components/buttons.css
index 479ca9cfcb..0786693699 100644
--- a/core/themes/seven/css/components/buttons.css
+++ b/core/themes/seven/css/components/buttons.css
@@ -62,7 +62,7 @@
 /* Prevent focus ring being covered by next siblings. */
 .button:focus {
   z-index: 10;
-  border: 1px solid #3AB2FF;
+  border: 1px solid #3ab2ff;
   box-shadow: 0 0 0.5em 0.1em hsla(203, 100%, 60%, 0.7);
 }
 .button:active {
@@ -94,7 +94,7 @@
   color: #fff;
 }
 .button--primary:focus {
-  border: 1px solid #1280DF;
+  border: 1px solid #1280df;
 }
 .button--primary:hover {
   box-shadow: 0 1px 2px hsla(203, 10%, 10%, 0.25);
diff --git a/core/themes/seven/css/components/dialog.css b/core/themes/seven/css/components/dialog.css
index 6d018208d1..a82f31ad98 100644
--- a/core/themes/seven/css/components/dialog.css
+++ b/core/themes/seven/css/components/dialog.css
@@ -29,7 +29,7 @@
   font-size: 1.231em;
   font-weight: 600;
   margin: 0;
-  color: #ffffff;
+  color: #fff;
   -webkit-font-smoothing: antialiased;
 }
 .ui-dialog .ui-dialog-titlebar-close {
@@ -51,7 +51,7 @@
   margin-top: -12px;
 }
 .ui-dialog .ui-widget-content.ui-dialog-content {
-  background: #ffffff;
+  background: #fff;
   overflow: auto;
   padding: 1em;
 }
diff --git a/core/themes/seven/css/components/dropbutton.component.css b/core/themes/seven/css/components/dropbutton.component.css
index 2cf014107f..001ef9a681 100644
--- a/core/themes/seven/css/components/dropbutton.component.css
+++ b/core/themes/seven/css/components/dropbutton.component.css
@@ -9,7 +9,7 @@
 .js .dropbutton .dropbutton-action > input,
 .js .dropbutton .dropbutton-action > a,
 .js .dropbutton .dropbutton-action > button {
-  color: #333333;
+  color: #333;
   text-decoration: none;
   padding: 0;
   margin: 0;
@@ -173,7 +173,7 @@
   background-color: #f2f1eb;
   background-image: -webkit-linear-gradient(top, #f6f6f3, #e7e7df);
   background-image: linear-gradient(to bottom, #f6f6f3, #e7e7df);
-  color: #333333;
+  color: #333;
   text-decoration: none;
   text-shadow: 0 1px hsla(0, 0%, 100%, 0.6);
   font-weight: 600;
diff --git a/core/themes/seven/css/components/field-ui.css b/core/themes/seven/css/components/field-ui.css
index 9dd396ed6d..85ade8329b 100644
--- a/core/themes/seven/css/components/field-ui.css
+++ b/core/themes/seven/css/components/field-ui.css
@@ -4,10 +4,10 @@
   padding: 1px 8px;
 }
 #field-display-overview tr.field-plugin-settings-changed {
-  background: #ffffbb;
+  background: #ffb;
 }
 #field-display-overview tr.drag {
-  background: #ffee77;
+  background: #fe7;
 }
 #field-display-overview tr.field-plugin-settings-editing {
   background: #d5e9f2;
diff --git a/core/themes/seven/css/components/jquery.ui/theme.css b/core/themes/seven/css/components/jquery.ui/theme.css
index dd81ec26a5..0ca067107c 100644
--- a/core/themes/seven/css/components/jquery.ui/theme.css
+++ b/core/themes/seven/css/components/jquery.ui/theme.css
@@ -347,8 +347,8 @@
 .ui-slider .ui-slider-handle {
   border: 1px solid #e4e4e4;
   border-bottom: 1px solid #b4b4b4;
-  border-left-color: #D2D2D2;
-  border-right-color: #D2D2D2;
+  border-left-color: #d2d2d2;
+  border-right-color: #d2d2d2;
   background-color: #e4e4e4;
   border-radius: 4px;
 }
@@ -375,16 +375,16 @@
  * Date Picker
  */
 .ui-datepicker {
-  border: 1px solid #A6A6A6;
-  background: #FFF;
+  border: 1px solid #a6a6a6;
+  background: #fff;
   /* Override datepicker.css */
   padding: 0;
 }
 
 /* Override tables.css */
 .ui-datepicker-calendar thead tr {
-  border-bottom: 1px solid #A6A6A6;
-  border-top: 1px solid #A6A6A6;
+  border-bottom: 1px solid #a6a6a6;
+  border-top: 1px solid #a6a6a6;
 }
 .ui-datepicker-calendar tr:hover {
   background: transparent;
diff --git a/core/themes/seven/css/components/system-status-counter.css b/core/themes/seven/css/components/system-status-counter.css
index 8d71965f01..ecba86700f 100644
--- a/core/themes/seven/css/components/system-status-counter.css
+++ b/core/themes/seven/css/components/system-status-counter.css
@@ -11,7 +11,7 @@
   display: inline-block;
   width: 100%;
   white-space: nowrap;
-  background: #FCFCFA;
+  background: #fcfcfa;
 }
 .system-status-counter__status-icon {
   display: inline-block;
diff --git a/core/themes/seven/css/components/tabs.css b/core/themes/seven/css/components/tabs.css
index 5aab30b849..fa3d585110 100644
--- a/core/themes/seven/css/components/tabs.css
+++ b/core/themes/seven/css/components/tabs.css
@@ -9,7 +9,7 @@
 .is-horizontal .tabs:before {
   content: '';
   display: block;
-  background-color: #A6A6A6;
+  background-color: #a6a6a6;
   height: 1px;
   position: absolute;
   bottom: 0;
@@ -86,7 +86,7 @@ li.tabs__tab a {
   z-index: 15;
   border-color: #a6a6a6;
   border-radius: 4px 0 0 0; /* LTR */
-  background-color: #ffffff;
+  background-color: #fff;
   color: #004f80;
 }
 [dir="rtl"] .tabs.primary .tabs__tab.is-active {
@@ -174,7 +174,7 @@ li.tabs__tab a {
 }
 .is-open .tabs__tab.is-active {
   border-color: #a6a6a6;
-  background-color: #ffffff;
+  background-color: #fff;
   color: #004f80;
   border-bottom: 1px solid #a6a6a6;
 }
diff --git a/core/themes/seven/css/components/tour.theme.css b/core/themes/seven/css/components/tour.theme.css
index d2ac5347c5..21d19aad66 100644
--- a/core/themes/seven/css/components/tour.theme.css
+++ b/core/themes/seven/css/components/tour.theme.css
@@ -72,30 +72,30 @@
   margin: 0;
 }
 .joyride-timer-indicator-wrap {
-  border: solid 1px rgba(255,255,255, 0.1);
+  border: solid 1px rgba(255, 255, 255, 0.1);
 }
 .joyride-timer-indicator {
-  background: rgba(255,255,255, 0.25);
+  background: rgba(255, 255, 255, 0.25);
 }
 
 .joyride-close-tip {
-  color: rgba(255,255,255, 0.4);
+  color: rgba(255, 255, 255, 0.4);
   text-decoration: none;
   font-size: 1.4em;
   font-weight: bold;
 }
 .joyride-close-tip:hover,
 .joyride-close-tip:focus {
-  color: rgba(255,255,255, 0.9);
+  color: rgba(255, 255, 255, 0.9);
   text-decoration: none;
 }
 
 .joyride-modal-bg {
-  background: rgba(0,0,0, 0.5);
+  background: rgba(0, 0, 0, 0.5);
 }
 
 .joyride-expose-wrapper {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 
 .joyride-expose-cover {
diff --git a/core/themes/seven/css/components/views-ui.css b/core/themes/seven/css/components/views-ui.css
index d212dd0bf9..a9face248a 100644
--- a/core/themes/seven/css/components/views-ui.css
+++ b/core/themes/seven/css/components/views-ui.css
@@ -157,7 +157,7 @@ details.fieldset-no-legend {
 /* @group Attachment details */
 
 #edit-display-settings-title {
-  color: #008BCB;
+  color: #008bcb;
 }
 
 /* @end */
@@ -189,7 +189,7 @@ details.fieldset-no-legend {
 .views-displays .secondary .open > a:hover,
 .views-displays .secondary .open > a:focus {
   background-color: #f1f1f1;
-  color: #008BCB;
+  color: #008bcb;
 }
 
 .views-displays .secondary .action-list li:first-child {
@@ -266,11 +266,11 @@ details.fieldset-no-legend {
 }
 
 .views-ui-rearrange-filter-form tr.drag td {
-  background-color: #FFEE77 !important;
+  background-color: #fe7 !important;
 }
 
 .views-ui-rearrange-filter-form tr.drag-previous td {
-  background-color: #FFFFBB !important;
+  background-color: #ffb !important;
 }
 
 /* @end */
diff --git a/core/themes/seven/css/theme/ckeditor-dialog.css b/core/themes/seven/css/theme/ckeditor-dialog.css
index b7d8dbbccb..70a137e6c6 100644
--- a/core/themes/seven/css/theme/ckeditor-dialog.css
+++ b/core/themes/seven/css/theme/ckeditor-dialog.css
@@ -192,11 +192,11 @@
   background-image: linear-gradient(to bottom, #fcfcfa, #e9e9dd);
   color: #1a1a1a;
   text-decoration: none;
-  box-shadow: 0 1px 2px hsla(0, 0%, 0%, 0.125)
+  box-shadow: 0 1px 2px hsla(0, 0%, 0%, 0.125);
 }
 .cke_reset_all .cke_dialog_footer_buttons a.cke_dialog_ui_button:focus {
   z-index: 10;
-  border: 1px solid #3AB2FF;
+  border: 1px solid #3ab2ff;
   box-shadow: 0 0 0.5em 0.1em hsla(203, 100%, 60%, 0.7);
 }
 .cke_reset_all .cke_dialog_footer_buttons a.cke_dialog_ui_button:active {
diff --git a/core/themes/stable/css/ckeditor/ckeditor.css b/core/themes/stable/css/ckeditor/ckeditor.css
index b4b1e16cec..bc2c43a6be 100644
--- a/core/themes/stable/css/ckeditor/ckeditor.css
+++ b/core/themes/stable/css/ckeditor/ckeditor.css
@@ -7,7 +7,7 @@
 
 .ckeditor-dialog-loading-link {
   border-radius: 0 0 5px 5px;
-  border: 1px solid #B6B6B6;
+  border: 1px solid #b6b6b6;
   border-top: none;
   background: white;
   padding: 3px 10px;
diff --git a/core/themes/stable/css/shortcut/shortcut.theme.css b/core/themes/stable/css/shortcut/shortcut.theme.css
index 73d58c6d46..3fe631c676 100644
--- a/core/themes/stable/css/shortcut/shortcut.theme.css
+++ b/core/themes/stable/css/shortcut/shortcut.theme.css
@@ -32,11 +32,11 @@
   margin-right: 0.3em;
 }
 .shortcut-action__message {
-  background: #000000;
+  background: #000;
   background: rgba(0, 0, 0, 0.5);
   border-radius: 5px;
   padding: 0 5px;
-  color: #ffffff;
+  color: #fff;
   display: inline-block;
   margin-left: 0.3em; /* LTR */
   opacity: 0;
diff --git a/core/themes/stable/css/system/system.admin.css b/core/themes/stable/css/system/system.admin.css
index 6f5f62b804..8893c53f7b 100644
--- a/core/themes/stable/css/system/system.admin.css
+++ b/core/themes/stable/css/system/system.admin.css
@@ -117,7 +117,7 @@ small .admin-link:after {
   text-transform: none;
 }
 .system-modules td details a {
-  color: #5C5C5B;
+  color: #5c5c5b;
   border: 0px;
 }
 .system-modules td details {
diff --git a/core/themes/stable/css/toolbar/toolbar.menu.css b/core/themes/stable/css/toolbar/toolbar.menu.css
index 099fb08496..479c78915f 100644
--- a/core/themes/stable/css/toolbar/toolbar.menu.css
+++ b/core/themes/stable/css/toolbar/toolbar.menu.css
@@ -46,38 +46,38 @@
  */
 .toolbar .level-2 > ul {
   background-color: #fafafa;
-  border-bottom-color: #cccccc;
+  border-bottom-color: #ccc;
   border-top-color: #e5e5e5;
 }
 .toolbar .level-3 > ul {
   background-color: #f5f5f5;
   border-bottom-color: #c5c5c5;
-  border-top-color: #dddddd;
+  border-top-color: #ddd;
 }
 .toolbar .level-4 > ul {
-  background-color: #eeeeee;
-  border-bottom-color: #bbbbbb;
+  background-color: #eee;
+  border-bottom-color: #bbb;
   border-top-color: #d5d5d5;
 }
 .toolbar .level-5 > ul {
   background-color: #e5e5e5;
   border-bottom-color: #b5b5b5;
-  border-top-color: #cccccc;
+  border-top-color: #ccc;
 }
 .toolbar .level-6 > ul {
-  background-color: #eeeeee;
-  border-bottom-color: #aaaaaa;
+  background-color: #eee;
+  border-bottom-color: #aaa;
   border-top-color: #c5c5c5;
 }
 .toolbar .level-7 > ul {
   background-color: #fafafa;
   border-bottom-color: #b5b5b5;
-  border-top-color: #cccccc;
+  border-top-color: #ccc;
 }
 .toolbar .level-8 > ul {
-  background-color: #dddddd;
-  border-bottom-color: #cccccc;
-  border-top-color: #dddddd;
+  background-color: #ddd;
+  border-bottom-color: #ccc;
+  border-top-color: #ddd;
 }
 
 /**
diff --git a/core/themes/stable/css/toolbar/toolbar.theme.css b/core/themes/stable/css/toolbar/toolbar.theme.css
index 0b3afc9876..7baf6963be 100644
--- a/core/themes/stable/css/toolbar/toolbar.theme.css
+++ b/core/themes/stable/css/toolbar/toolbar.theme.css
@@ -31,13 +31,13 @@
 .toolbar .toolbar-bar {
   background-color: #0f0f0f;
   box-shadow: -1px 0 3px 1px rgba(0, 0, 0, 0.3333); /* LTR */
-  color: #dddddd;
+  color: #ddd;
 }
 [dir="rtl"] .toolbar .toolbar-bar {
   box-shadow: 1px 0 3px 1px rgba(0, 0, 0, 0.3333);
 }
 .toolbar .toolbar-bar .toolbar-item {
-  color: #ffffff;
+  color: #fff;
 }
 .toolbar .toolbar-bar .toolbar-tab > .toolbar-item {
   font-weight: bold;
@@ -56,7 +56,7 @@
  * Toolbar tray.
  */
 .toolbar .toolbar-tray {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 .toolbar .toolbar-tray-horizontal > .toolbar-lining {
   padding-right: 5em; /* LTR */
@@ -67,16 +67,16 @@
 }
 .toolbar .toolbar-tray-vertical {
   background-color: #f5f5f5;
-  border-right: 1px solid #aaaaaa; /* LTR */
+  border-right: 1px solid #aaa; /* LTR */
   box-shadow: -1px 0 5px 2px rgba(0, 0, 0, 0.3333); /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-vertical {
-  border-left: 1px solid #aaaaaa;
+  border-left: 1px solid #aaa;
   border-right: 0 none;
   box-shadow: 1px 0 5px 2px rgba(0, 0, 0, 0.3333);
 }
 .toolbar .toolbar-tray-horizontal {
-  border-bottom: 1px solid #aaaaaa;
+  border-bottom: 1px solid #aaa;
   box-shadow: -2px 1px 3px 1px rgba(0, 0, 0, 0.3333); /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal {
@@ -99,33 +99,33 @@
   text-decoration: underline;
 }
 .toolbar .toolbar-menu {
-  background-color: #ffffff;
+  background-color: #fff;
 }
 .toolbar .toolbar-tray-horizontal .menu-item + .menu-item {
-  border-left: 1px solid #dddddd; /* LTR */
+  border-left: 1px solid #ddd; /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal .menu-item + .menu-item {
   border-left: 0 none;
-  border-right: 1px solid #dddddd;
+  border-right: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-horizontal .menu-item:last-child {
-  border-right: 1px solid #dddddd; /* LTR */
+  border-right: 1px solid #ddd; /* LTR */
 }
 [dir="rtl"] .toolbar .toolbar-tray-horizontal .menu-item:last-child {
-  border-left: 1px solid #dddddd;
+  border-left: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item + .menu-item {
-  border-top: 1px solid #dddddd;
+  border-top: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item:last-child {
-  border-bottom: 1px solid #dddddd;
+  border-bottom: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item .menu-item {
   border: 0 none;
 }
 .toolbar .toolbar-tray-vertical .toolbar-menu ul ul {
-  border-bottom: 1px solid #dddddd;
-  border-top: 1px solid #dddddd;
+  border-bottom: 1px solid #ddd;
+  border-top: 1px solid #ddd;
 }
 .toolbar .toolbar-tray-vertical .menu-item:last-child > ul {
   border-bottom: 0;
diff --git a/core/themes/stable/css/views_ui/views_ui.admin.theme.css b/core/themes/stable/css/views_ui/views_ui.admin.theme.css
index b843586ad4..53a08d1450 100644
--- a/core/themes/stable/css/views_ui/views_ui.admin.theme.css
+++ b/core/themes/stable/css/views_ui/views_ui.admin.theme.css
@@ -623,10 +623,10 @@ td.group-title {
   border: none;
 }
 .views-ui-dialog .views-offset-top {
-  border-bottom: 1px solid #CCC;
+  border-bottom: 1px solid #ccc;
 }
 .views-ui-dialog .views-offset-bottom {
-  border-top: 1px solid #CCC;
+  border-top: 1px solid #ccc;
 }
 .views-ui-dialog .views-override > * {
   margin: 0;