I have two minor suggestions which I think will improve the user experience:
1. Code highlightning - add a box which shows an example of how the code will look like with the new colors added:
2. ability to disable short-hand when writing CSS:
The reason for this is that I can't seem to get WB2014 to add a simi-colon (;) after I have made an attribute using the Auto Complete and after a while this get pretty annoying, however, I suspect that my suggestion would make it hard for users who prefer to write CSS in short-hand and that is why I'm suggestion this option.