[frio] Add dynamic CSS property before introducing accented themes

- Introduce variables for font colors
- Set content background transparency on several background colors
- Change radio/checkbox colors depending on the link color
- Prevent post highlighting to end up on static white

view/theme/frio/js/theme.js

@@ -702,7 +702,7 @@ function scrollToItem(elementId) {
 		scrollTop: itemPos
 	}, 400).promise().done( function() {
 		// Highlight post/commenent with ID  (GUID)
-		$el.animate(colWhite, 1000).animate(colShiny).animate(colWhite, 600);
+		$el.animate(colWhite, 1000).animate(colShiny).animate({backgroundColor: 'transparent'}, 600);
 	});
 }