perhaps very small prints that read as solids.
Your real difficulty is finding the fabric. It will take a long time searching (I've had the experience) You could use hand dyes but they usually come in 8 gradations.
You will have to calculate the amount of yardage needed and then start the search. Couple weeks ago I was in a very large quilt shop with hundreds of bolts of fabric in each color group and I doubt that I could have put together 12 suitable values of any color. I recently did a Giant Dahlia that needed 6 colors but 8 values in each color and it took me almost years to find the fabric. This is not to discourage but to warn. Go for it. It is a great design.