Been there, done that. I just grab squares from a pile, trying to get one light then one dark and sew them together. If two end up side by side, so what? It will make someone smile and say,Oh look, she made a mistake,ha ha. We make and tie scrappy quilts for charity and no one has returned any because there were two alike side by side. Have fun, let your hair down and sew away. I love all the different colors, designs and fabrics, we make them to get things done. When sewing for charity, quantity is more important than matching squares. You won't win any prizes but someone will be grateful for a warm quilt of many colors.
Carol J.