Someone just mentioned in a different post that it is a good idea to use same color on top and bottom. I FMQ a quilt for my DH for Christmas last year and had a problem with the yellow I was using on the bottom showing on the top where it was black. I fussed with the tension and got it the best I could, and then when I was done, I went back and hand colored where the light showed in the black with a black pigma pen.
Good luck.