stand back and squint your eyes or if you wear glasses, take them off and look
Don't spend too much time with the decision. Toss them in a pile, rearrange as your "gut" tells you to and go with it. You could spend the rest of the year trying to get "just the right" comgination. You can analyze and re-analyze and the last arrangement won't be any better than the first.
I taught classes in watercolor quilts and know how this works.