I like to use a color wheel, it can help with picking out colors. Usually I just use the focus fabric or what I like. Something I neglected to do, which would've prevented a goof on my DH quilt-I couldn't decide which green to use in between star points- ended up using one too dark and the star is not as visible as it should be. I should have made a black and white copy of the greens I was considering. You can tell value that way. Lesson learned.