Bug 1424100 - Make panel instructions color consistent with sidebar. r=eoger

MozReview-Commit-ID: E9RnHaonulr

--HG--
extra : rebase_source : 443ea6e56b3da6dd91c1f3343fce023be2539ac8

browser/themes/shared/customizableui/panelUI.inc.css

@@ -609,7 +609,7 @@ toolbarbutton[constrain-size="true"][cui-areatype="menu-panel"] > .toolbarbutton
   text-align: center;
   text-shadow: none;
   max-width: 15em;
-  color: GrayText;
+  color: rgba(12, 12, 13, 0.5);
 }
 
 /* The boxes with "instructions" get extra top and bottom padding for space