You might try a bridal shop. They have to dye things to match quite often. If you insist on doing it yourself, be sure to follow the instructions to the letter. I'll add that whenever I dye muslin for one of my stage sets, I usually add some salt to the water. I was told a long time ago that you must have salted water (not much, a teaspoon for a large pot) to make the cotton fibers open up to take the dye. YMMV.