When I am working on a BOM, I usually go with similar colors to what is shown. I figure they have worked out what looks good next to the blocks around it and will have the colors scattered around the quilt. I do have a tendency to go with tone on tone and blender fabrics. If I want to use a print fabric, I go for patterns that show off the prints with solids around it. If I have a fat quarter bundle, I throw in solids and blenders to work into the pattern. If it's mostly patterns, I go for what's large, medium and small prints and try to work them around each other. No large prints next to large prints. I think the eye needs a place to rest.