Brand red still used in several places that should be blue

[kadamwhite]

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.

[CoreyBenefiel]

Very patriotic.

[robindevitt]

Posting here for the arrows in pagination

[robindevitt]

Realise I missed a couple more items, can get a second PR later this week 👍🏼

[CoreyBenefiel]

Thanks @robindevitt