Update selectors

chrome/userChrome.css

 #TabsToolbar #firefox-view-button { filter: grayscale(1); }
 
 /* Set private browsing icon to grayscale */
-#private-browsing-indicator-with-label > image.private-browsing-indicator-icon { filter: grayscale(1) invert(); }
+#TabsToolbar .private-browsing-indicator-with-label > image.private-browsing-indicator-icon { filter: grayscale(1) invert(); }
 
 /* Hide private browsing label */
-#private-browsing-indicator-with-label > label { display: none; }
+#TabsToolbar .private-browsing-indicator-with-label > label.private-browsing-indicator-label { display: none; }
 
 /* Hide tab bar spacer */
 #TabsToolbar .titlebar-spacer[type="post-tabs"] { display: none; }