A good way to tell if there is enough contract is to take a photo of them together and change the photo to sepia or black/white on your computer unless you can do that on your camera. This will show you the contract between the fabrics. Or if you have a piece of tinted plexiglas or glass put it over the fabrics as it will change how you see the colors. I find if I dim the lights just right, I can get a better concept of the contrast or lack there of. I do this when I have my blocks up on the design wall and am wondering if I have them arranged correctly. Can see the lights and darks better this way. Just a suggestion.