diff -u b/core/modules/color/color.module b/core/modules/color/color.module
--- b/core/modules/color/color.module
+++ b/core/modules/color/color.module
@@ -63,7 +63,6 @@
       '#theme' => 'color_scheme_form',
     ];
     $form['color'] += color_scheme_form($form, $form_state, $theme);
-    $form['#validate'][] = 'color_scheme_form_validate';
     // Ensure color submission happens first so we can unset extra values.
     array_unshift($form['#submit'], 'color_scheme_form_submit');
   }
@@ -180,7 +179,6 @@
  * @param $theme
  *   The machine name of the theme whose color settings are being configured.
  *
- * @see color_scheme_form_validate()
  * @see color_scheme_form_submit()
  */
 function color_scheme_form($complete_form, FormStateInterface $form_state, $theme) {
@@ -338,23 +336,7 @@
 }
 
 /**
- * Form validation handler for color_scheme_form().
- *
- * @see color_scheme_form_submit()
- */
-function color_scheme_form_validate($form, FormStateInterface $form_state) {
-  // Only accept hexadecimal CSS color strings to avoid XSS upon use.
-  foreach ($form_state->getValue('palette') as $key => $color) {
-    if (!color_valid_hexadecimal_string($color)) {
-      $form_state->setErrorByName('palette][' . $key, t('You must enter a valid hexadecimal color value for %name.', ['%name' => $form['color']['palette'][$key]['#title']]));
-    }
-  }
-}
-
-/**
  * Form submission handler for color_scheme_form().
- *
- * @see color_scheme_form_validate()
  */
 function color_scheme_form_submit($form, FormStateInterface $form_state) {
 
only in patch2:
unchanged:
--- a/core/modules/color/tests/src/Functional/ColorTest.php
+++ b/core/modules/color/tests/src/Functional/ColorTest.php
@@ -81,7 +81,7 @@ protected function setUp(): void {
       '#00' => FALSE,
       '#0000' => FALSE,
       '#00000' => FALSE,
-      '123456' => FALSE,
+      '123456' => TRUE,
       '#00000g' => FALSE,
     ];
   }
@@ -174,7 +174,7 @@ public function testValidColor() {
         $this->assertText('The configuration options have been saved.');
       }
       else {
-        $this->assertText('You must enter a valid hexadecimal color value for Main background.');
+        $this->assertText('Main background must be a valid color.');
       }
     }
   }