Use sass properly for dark mode styling.

Make labels grey if not highlighted, black if highlighted.
Properly address contrasts in dark mode - change property value colors to lighter versions to avoid bad contrast with diff colors, maintain white text for dark mode where relevant.
Improve contrasts of current/selected elements.

Screencast: https://screencast.googleplex.com/cast/NTkxNjU2MjU0MzM0NTY2NHwwOTcyZjVlYS1mOQ

Fixes: 339793583
Test: n/a
Change-Id: I3e6abd279606202d94b05d104a8b67866fc8065d
15 files changed