diff --git a/colorbox.api.php b/colorbox.api.php
index 4fda7ee..47e37cd 100644
--- a/colorbox.api.php
+++ b/colorbox.api.php
@@ -31,3 +31,19 @@ function hook_colorbox_settings_alter(&$settings, &$style) {
     $style = 'mystyle';
   }
 }
+
+/**
+ * Provides the ability to add new colorbox styles.
+ *
+ * The key for you styles should be in the format of module_name/library_name,
+ * where library_name is the name of your stylesheet in your libraries.yml file.
+ *
+ * If the style isn't defined properly, it will not be listed or added.
+ *
+ * Implements hook_colorbox_styles().
+ */
+function hook_colorbox_styles() {
+  return [
+    'mymodule/library_name' => 'Style Name',
+  ];
+}
diff --git a/colorbox.install b/colorbox.install
index 50c69cd..4d48ce4 100644
--- a/colorbox.install
+++ b/colorbox.install
@@ -37,3 +37,15 @@ function colorbox_requirements($phase) {
     ],
   ];
 }
+
+/**
+ * Change the colorbox.settings.style variable to be module/library format.
+ */
+function colorbox_update_8001() {
+  $config = \Drupal::configFactory()->getEditable('colorbox.settings');
+  $colorbox_style = $config->get('custom.style');
+  // Add colorbox prefix if needed, change none to empty string.
+  $new_style = $colorbox_style != 'none' ? 'colorbox/' . $colorbox_style : '';
+  $config->set('custom.style', $new_style);
+  $config->save();
+}
diff --git a/colorbox.theme.inc b/colorbox.theme.inc
index 2e58fe6..2aa06f1 100644
--- a/colorbox.theme.inc
+++ b/colorbox.theme.inc
@@ -83,7 +83,7 @@ function template_preprocess_colorbox_formatter(&$variables) {
   // Shorten the caption for the example styles or when caption
   // shortening is active.
   $config = \Drupal::config('colorbox.settings');
-  $colorbox_style = $config->get('colorbox_style');
+  $colorbox_style = $config->get('custom.style');
   $trim_length = $config->get('colorbox_caption_trim_length');
   if (((strpos($colorbox_style, 'colorbox/example') !== FALSE) || $config->get('colorbox_caption_trim')) && (Unicode::strlen($caption) > $trim_length)) {
     $caption = Unicode::substr($caption, 0, $trim_length - 5) . '...';
diff --git a/src/ColorboxAttachment.php b/src/ColorboxAttachment.php
index 81a9a9f..5742528 100644
--- a/src/ColorboxAttachment.php
+++ b/src/ColorboxAttachment.php
@@ -112,9 +112,21 @@ class ColorboxAttachment implements ElementAttachmentInterface {
       $page['#attached']['library'][] = 'colorbox/colorbox-dev';
     }
 
-    // Add JS and CSS based on selected style.
-    if ($style != 'none') {
-      $page['#attached']['library'][] = "colorbox/$style";
+    // Add JS and CSS based on selected style library, but only if correct format.
+    if (!empty($style)) {
+      // If not using a colorbox library, add colorbox init.
+      if (strpos($style, 'colorbox/') === FALSE) {
+        $page['#attached']['library'][] = "colorbox/init";
+      }
+
+      $parts = explode('/', $style);
+      if (count($parts) == 2) {
+        $page['#attached']['library'][] = $style;
+      }
+      // Log warning if style is invalid.
+      else {
+        \Drupal::logger('colorbox')->notice($this->t('Attempt to load invalid style %name. Styles need to be defined in format module/library_name.', array('%name' => $style)));
+      }
     }
     else {
       $page['#attached']['library'][] = "colorbox/init";
diff --git a/src/Form/ColorboxSettingsForm.php b/src/Form/ColorboxSettingsForm.php
index ed54747..6709559 100644
--- a/src/Form/ColorboxSettingsForm.php
+++ b/src/Form/ColorboxSettingsForm.php
@@ -74,17 +74,30 @@ class ColorboxSettingsForm extends ConfigFormBase {
       '#title' => $this->t('Styles and options'),
       '#open' => TRUE,
     ];
+
     $colorbox_styles = [
-      'default' => $this->t('Default'),
-      'plain' => $this->t('Plain (mainly for images)'),
-      'stockholmsyndrome' => $this->t('Stockholm Syndrome'),
-      'example1' => $this->t('Example 1'),
-      'example2' => $this->t('Example 2'),
-      'example3' => $this->t('Example 3'),
-      'example4' => $this->t('Example 4'),
-      'example5' => $this->t('Example 5'),
-      'none' => $this->t('None'),
-    ];
+      'colorbox/default' => $this->t('Default'),
+      'colorbox/plain' => $this->t('Plain (mainly for images)'),
+      'colorbox/stockholmsyndrome' => $this->t('Stockholm Syndrome'),
+      'colorbox/example1' => $this->t('Example 1'),
+      'colorbox/example2' => $this->t('Example 2'),
+      'colorbox/example3' => $this->t('Example 3'),
+      'colorbox/example4' => $this->t('Example 4'),
+      'colorbox/example5' => $this->t('Example 5'),
+      '' => $this->t('None'),
+    ];
+    // Add any custom styles.
+    $custom_styles = \Drupal::moduleHandler()->invokeAll('colorbox_styles');
+    if (!empty($custom_styles) && is_array($custom_styles)) {
+      foreach ($custom_styles as $library => $name) {
+        // If not in module/library format, remove it.
+        $parts = explode('/', $library);
+        if (count($parts) != 2) {
+          unset($custom_styles[$library]);
+        }
+      }
+      $colorbox_styles += $custom_styles;
+    }
     $form['colorbox_custom_settings']['colorbox_style'] = [
       '#type' => 'select',
       '#title' => $this->t('Style'),