Updates the error/notice box with cleaner look, softer colors.

Summary: These colors are more inline with the look and feel and match the table colors.

Test Plan: Used Inspect Element to test each color combination on an error page.

Reviewers: epriestley, btrahan

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4593