R1:0376373ee09a

Use standard colors for timeline anchor target

Summary: Still highlighted, less brightly

Test Plan:
{F149972}

{F149973}

test minor and major events.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D8956