Bug 1509631 - Fix identity popup expander color. r=johannh

Differential Revision: https://phabricator.services.mozilla.com/D15811

--HG--
extra : moz-landing-system : lando

browser/themes/shared/controlcenter/panel.inc.css

@@ -114,7 +114,7 @@
   background-size: 16px, auto;
   -moz-context-properties: fill;
   fill: currentColor;
-  color: inherit;
+  color: inherit !important; /* !important overrides :hover and :active:hover colors from button.css on Mac and Linux */
 }
 
 .identity-popup-expander:-moz-locale-dir(ltr) {