USWDS: The United States Web Design System
Anyone with any part in designing user interfaces seriously needs to commit their section on color to heart: 
<a href="https:&#x2F;&#x2F;designsystem.digital.gov&#x2F;design-tokens&#x2F;color&#x2F;overview&#x2F;" rel="nofollow">https:&#x2F;&#x2F;designsystem.digital.gov&#x2F;design-tokens&#x2F;color&#x2F;overvie...</a><p>Especially the contrast&#x2F;magic number discussion.  It&#x27;s crazy how many user interfaces these days blur design elements to where you can&#x27;t tell were controls are.  The recent trend to eliminate window title bars is particularly infuriating, but buttons that don&#x27;t look like buttons because they blend into the background are another pet peeve - or have light gray on dark gray. Ugh!  Contrast serves a purpose!