CKEditor's "available buttons" are managed through admin/config/content/formats/manage/content_format the icons in the "available buttons" and "active toolbar" component are completely invisible.
Probably all of these buttons should be done with SVG files rather than background images.
Something like:
https://www.drupal.org/files/issues/2025-07-04/strikethrough-svgrepo-com... →
Or just use UTF characters like:
<span class="ckeditor5-toolbar-button ckeditor5-toolbar-button-bold">
<span class="visually-hidden">Bold</span>
<span class="forced-colors-label">B</span>
</span>
I've uploaded a bunch of possible UTF8 codes → other ones we could use here.
Active
11.2 🔥
ckeditor.module
It affects the ability of people with disabilities or special needs (such as blindness or color-blindness) to use Drupal.