Administration: Standardize colors used in CSS to a single palette.

This is part of a larger project in cleaning up core's admin CSS. This collapses all colors used in the CSS to one of 12 blues, greens, reds, and yellows, 13 grays, pure black, and pure white. The colors are perceptually uniform from light to dark, half of each range has a 4.5 or higher contrast against white, the other half has a 4.5 or higher contrast against black.

Standardizing on this set of colors will help contributors make consistent, accessible design decisions. The full color palette can be seen here: https://codepen.io/ryelle/full/WNGVEjw

Props notlaura, danfarrow, kburgoine, drw158, audrasjb, Joen, hedgefield, ibdz, melchoyce.
See #49999.



git-svn-id: https://develop.svn.wordpress.org/trunk@50025 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/general-template.php

@@ -4392,10 +4392,10 @@ function register_admin_color_schemes() {
 		'fresh',
 		_x( 'Default', 'admin color scheme' ),
 		false,
-		array( '#222', '#333', '#0073aa', '#00a0d2' ),
+		array( '#1d2327', '#2c3338', '#3582c4', '#72aee6' ),
 		array(
-			'base'    => '#a0a5aa',
-			'focus'   => '#00a0d2',
+			'base'    => '#a7aaad',
+			'focus'   => '#72aee6',
 			'current' => '#fff',
 		)
 	);