Thanks for all the replies!
I think I will use the light purple for the background for the appliqué cupcake blocks.
Now for the filler blocks. Thinking about using the same purple, and some of the other 2 purples to make 9 patch? Or 4 patch? Or a rail fence maybe? The blocks will be 7", so I don't think just plain squares of fabric will look good.
Thanks for all your help, kim