R1:d9ab267de601

Darken Crumb border

Summary: This border is meant to be darker, make it relative to background color.

Test Plan: Test and see new darker border.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13564