Accessibility: Administration: Correct active button color for the alternative color schemes.

Follow-up to [46815].

Props melchoyce, ryelle, larrach, audrasjb, studiotwee, afercia, azaozz.
Fixes #48598.
Built from https://develop.svn.wordpress.org/trunk@46817


git-svn-id: https://core.svn.wordpress.org/trunk@46617 1a063a9b-81f0-0310-95a4-ce76da25c4cd