Yeah, looking at it on my PC now, and it looks fine. (very nice!)
Personally speaking, I've always used individual images for different colors for things like this, as it's a guarantee you won't run into this kind of compatibility issue.
Not using this method would be easy for changing the colours of the box. However, the text is also changed this way and because the text itself changes along with the colour of the text, converting all possible outcomes to images for compatibility issues would result in 81 different images for the text which for me is not something which is worth the sacrifice.
If the text doesn't take this change then I see no point applying it to the boxes as well.
If anyone has an alternative to this please tell me as it would be very appreciated