Minor Differential CSS

Summary: More Diffusion/Differential touch ups, ToC, etc.

Test Plan: Look at colors, see that they match or look better.

Reviewers: epriestley, btrahan

Reviewed By: btrahan

CC: Korvin, epriestley, aran

Maniphest Tasks: T3952

Differential Revision: https://secure.phabricator.com/D7386