Accessibility: Improve the color contrast ratio replacing the residual occurrences of the #777 gray.

Uses the existing `#72777c` on white backgrounds and the new `#555d66` "dark medium gray" on darker backgrounds.

Fixes #35605.
Built from https://develop.svn.wordpress.org/trunk@36396


git-svn-id: http://core.svn.wordpress.org/trunk@36363 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/widgets.css

@@ -114,7 +114,12 @@
 	padding: 0 0 15px;
 	margin: 0;
 	font-style: normal;
-	color: #777;
+	color: #72777c;
+}
+
+.widget-holder .description,
+.inactive-sidebar .description {
+	color: #555d66;
 }
 
 #widgets-right .widgets-holder-wrap .description {
@@ -282,7 +287,7 @@ div#widgets-right .closed .widgets-sortables {
 
 /* Dragging a widget over a closed sidebar */
 #widgets-right .widgets-holder-wrap.widget-hover {
-	border-color: #777;
+	border-color: #72777c;
 	-webkit-box-shadow: 0 1px 2px rgba(0,0,0,0.3);
 	box-shadow: 0 1px 2px rgba(0,0,0,0.3);
 }