What I would do is off the wall. When all else fails; I would cut small pieces of the first choice and glue them to a piece of copy paper. Do the same with the second choice on the same paper etc.. Make a copy of the fabrics and when you look at the new copy, pick the fabrics which have the most contrast. Medium, dark and lights show up better on the copy. When the eye is tricked, the copy never lies. I understand you did not ask about contrast, but it needs to be considered, also.