Nope, but thanks for looking.
Oddly, I've just switched my pc on and the colour is now showing correctly 
The top one the same grey as the background, and the lower one a darker grey - which is what I wanted. Earlier I did the usual trick of turning things to a bright colour one by one to see where it was.
Hmmm, wonder if the no-show is a SkinStudio/WB bug not applying the skin properly? Anyway, it's ok now.
