Taking colors from a print is definitely helpful, especially when you can compare color dots from the selvages.
For those who are color blind, can you use more than two fabrics by adding some neutrals to add contrast? I'm not color blind, but both of my sons are, so this is definitely of interest to me. I also wonder whether you can use more fabrics if you have a more scrappy, but monochromatic quilt, like various blue fabrics paired with white.