Quilting Panda, I've made many sampler type quilts, and several BOOM quilts where I get fabric selected from lots of other people. I've found the only time something looks out of place is if it's the only block that uses an odd color. As long as there are an assortment of blocks using each of the color shades, they should end up fine. I tend to move toward getting too "matchy" with my sampler and scrap quilts, and then I loose the randomness that I'm going for to start with. So I have to fight against that and let in more variation.