Update Twenty Fifteen's `colorScheme` control to properly interact with the API, using `wp.customize.control()` instead of traversing DOM for other controls' container elements and stop manually updating color control UIs.
props westonruter.
fixes#30031.
git-svn-id: https://develop.svn.wordpress.org/trunk@30126 602fd350-edb4-49c9-b593-d223f7449a82