If you're buying a painted roving or painting your own, you may want to think about staple length and color repeats. If your color repeat is shorter than your fiber length, it will be difficult to get enough fibers to spin a relatively pure color in a repeat. If you want a variety of color or a heathered color, the shorter color repeats are fine. Some one jump in and comment on this section. I have a feeling I didn't explain it adequately. Here's a picture that might help.