6 files declare their use of Color in Zircon Profile 8

Color.php in core/lib/Drupal/Core/Render/Element/Color.php

Contains \Drupal\Core\Render\Element\Color.

ColorTest.php in core/tests/Drupal/Tests/Component/Utility/ColorTest.php

Contains \Drupal\Tests\Component\Utility\ColorTest.

CreateNew.php in core/modules/system/src/Plugin/ImageToolkit/Operation/gd/CreateNew.php

Contains \Drupal\system\Plugin\ImageToolkit\Operation\gd\CreateNew.

GDToolkit.php in core/modules/system/src/Plugin/ImageToolkit/GDToolkit.php

Contains \Drupal\system\Plugin\ImageToolkit\GDToolkit.

Rotate.php in core/modules/system/src/Plugin/ImageToolkit/Operation/gd/Rotate.php

Contains \Drupal\system\Plugin\ImageToolkit\Operation\gd\Rotate.

RotateImageEffect.php in core/modules/image/src/Plugin/ImageEffect/RotateImageEffect.php

Contains \Drupal\image\Plugin\ImageEffect\RotateImageEffect.