Fullscreen API changes, color settings tweaks

demo/src/sass/settings/colors.scss

@@ -24,5 +24,9 @@ $color-vimeo: #19b7ed;
 $color-link: #fff;
 $color-background: $color-brand-primary;
 
+// Buttons
+$color-button-background: #fff;
+$color-button-text: $gray;
+
 // Focus
 $tab-focus-default-color: #fff;