my friend Dorothy does all my prep work for me and she brings her ideas to the table on colors. I tend to lean toward prints with a white to cream background matched with a like colors med to dark prints. she is more of the ah heck just throw it in version. LOL
so she has done some combinations of med/darks and med/ med. they have their place in the scheme of things for me but I still tend to use more of the light / darks.
When making Bostons I do usually prefer light/med for the top and dark for the bottoms. but in some designs that goes out hte window and the pattern may call for a light on the bottom and two meds for the top quarter sqs.