[Redesign] Anchor blue

Summary: Use a consistent blue across all anchors. Slightly lighter than current blue. Ref T8099

Test Plan: Visit Phriction, Remarkup, various apps.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12918