MediaWiki theme: Replace static `color` value with Less variable
MediaWiki theme: Replace static `color` value with Less variable

Replacing `color` value in windowManager with Less variable.

Change-Id: I5e96ad291cfb1ce5dc28176e77d55a47b8f7a364

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui