Update work tab colors and fab background color

Spec: https://screenshot.googleplex.com/6mKVuFNNNQfXpbD

bug: 283120562
test:
manually Launcher3 build var:
worktab lt: https://screenshot.googleplex.com/B8v44jm77o5Jyc7
widgetpicker tab lt: https://screenshot.googleplex.com/48WjAB8fKpZSEQ7
sharesheet tab lt: https://screenshot.googleplex.com/9rfSBeNALXbG7NL
worktab dt: https://screenshot.googleplex.com/332jCxde9vDW7hd
widgetpicker tab dt: https://screenshot.googleplex.com/3PGtrvQ2jLhQD4k
sharesheet tab dt: https://screenshot.googleplex.com/3jr4GPzRc3rzMA6

NexusLauncher:
worktab lt: https://screenshot.googleplex.com/BH2SFMXfQ4dtBeh
sharesheet lt: https://screenshot.googleplex.com/5axg34QgTt87iSL
widget picker tab lt: https://screenshot.googleplex.com/928kWFJ5mTun9py
worktab dt: https://screenshot.googleplex.com/7KWKLH4kt6nJpXT
sharesheet dt: https://screenshot.googleplex.com/778UoyhYrhimSAz
widgetpicker tab dt: https://screenshot.googleplex.com/FFFxBLqsATNXj8v

Change-Id: I78f20b2863a04d23e8a8880fc1d6a3ac0cfeb82a