I had trouble picking fabrics for a Bonnie mystery until I paid attention to value. If she uses a bright...I use a bright. If she uses a dark, I use a dark. My problem comes when I use something like yellow that can get muddled or disappear if its next to a light/neutral. I have a small plastic spatula that is clear red. If I cannot decide if its a light/med/dark, I look at it thru the spatula! A medium can become a light if its next to a deep dark color or it can be a dark when its next to light/white. When I started I had ALOT to learn about color and value! I still learn something on EVERY quilt. Some quilts I like better than others...but I LOVE to make 'em all!