Soften diff backgrounds.

Figma screenshot: https://screenshot.googleplex.com/9Xs5WqDYHD6Djds

Final screenshots:
https://screenshot.googleplex.com/SH44WZSBJQUarEa
https://screenshot.googleplex.com/3FkwPWP9Rdb6xVv
https://screenshot.googleplex.com/6UvxRQLhLMdBdrQ
https://screenshot.googleplex.com/AqTnaHKziDkY9Li
https://screenshot.googleplex.com/7PWaCACUUBzG2m6
https://screenshot.googleplex.com/4biNwoWraY3qAeW

Bug: 360336024
Test: n/a
Change-Id: I08dabe551a8a92169a78aeac6d5a30179bfab852
3 files changed