Brand red still used in several places that should be blue

## Issue Description

Following humanmade/hm-pattern-library#173 and #568, the main UI color for H2 pages shifted away from the lighter brand red to a more-legible blue. However, I've noticed a few areas I missed:

- Pill button dropdowns
- Tabs in comment and post editor
- Upload an Attachment link

There may be others, as well. This issue serves to capture that these should be unified with the other UI elements and turned blue.