For me, they don't need a color scheme as much as they need a theme. Batiks, 30's, solids with lots of neutrals to bind them together. But beauty is in the eye of the beholder. I like to also mix up the neutrals, then if I have to add more, it doesn't conflict as to old blocks and new blocks. Different light almond/grey batiks or different whites. One or two different colors doesn't work. It has to be at least 5 different neutrals to add interest and depth.