When the UI got updated in the past, it was reported as a bug and never fixed.

A side note on mobile the UI is the same for all site, as such the color are better suited for question with accepted answer

See there for example; https://meta.serverfault.com/a/8027/126632

A report I did in the past too; https://meta.serverfault.com/questions/8209/sf-layout-answer-coloring