[Redesign] Add back limited header-color options

Summary: Ref T8099. Adds back basic header color options, which change the logo color instead. Also RAINBOW.

Test Plan:
tested each of the new colors.

{F442284}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13040

scripts/celerity/generate_sprites.php

@@ -29,7 +29,6 @@ $generator = new CeleritySpriteGenerator();
 $sheets = array(
   'menu' => $generator->buildMenuSheet(),
   'tokens' => $generator->buildTokenSheet(),
-  'main-header' => $generator->buildMainHeaderSheet(),
   'login' => $generator->buildLoginSheet(),
   'projects' => $generator->buildProjectsSheet(),
 );