While using the coverage tool I really wanted to see used code with green (and unused css with red).

As a point of reference, see this image search of code coverage tools: https://www.google.com/search?q=code+coverage&source=lnms&tbm=isch&sa=X#tbm=isch&q=code+coverage+annotation
All are doing red and green highlights.

Without this, I feel skeptical that the tool is telling me the truth. 

Also, whitespace and comments (outside rules) should be left white, as most coverage tools do.

valih, does that makes sense?