Just tested it; works fine.oh, while i'm here, Droid i don't really know what's up, but even when i match ANY yellows it just charges my RED skill???? i'm playing whatever is current on steam btw (0.6.3).....
At a guess you've got a Red/Yellow skill in a higher slot (that will take both red AND yellow) and that's eating the yellows that you are filling it with.
Angelic Denial is yellow
Vulcanic Blast is Red
Rejuvination is Red/Yellow