Add Indigo header, fix colors and hovers

Summary: This adds Phacility "Indigo" as well as uses rgba for colors and hovers improving icon colors.

Test Plan:
Tested each color and hover states. Set test instance to scootaloo.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11836