<element id="Panel.StarRating.Highlight" bg="255,245,63" bg2="255,230,48" fg="50,50,50" fg2="50,50,50" />
add 'bg' and 'bg2' to starrating. (I'm not sure this trick will always work)
With extremer colors it doesn't seem to work well, then they 'strenghten' each other. For perfection transparency is probably required, but I don't know how that would work.