sometimes, I just let the size of the scrap fabric decide for me what specific fabric to use in the color group of the clue. So I start with the smaller fabrics and cut into the bigger ones as I run out. After all, this is supposed to be a "scrap" quilt so that is what I use up first. However, as it goes along, I may start cutting from a number of different ones to keep the scrappy look. for example on one of the previous mysteries.....I only had 5 different fabrics left, so I cut some from each for the clue, but the pieces in the quilt are usually so small, it probably doesn't matter much.