Update app pair icon colors when switching containers

This CL updates the color for the app pair background, and adds a way for an app pair icon to redraw as a different color when switching containers.

Bug: 315731527
Flag: ACONFIG com.android.wm.shell.enable_app_pairs TRUNKFOOD
Test: Manual
Change-Id: I615cb95d51f7c4c120ad306246d9491bf4452229