After a little experimentation, I decided to go with the purple. It doesn't look as good, IMO, BUT I can see the stitches on the back easier and can tell when they're not the same as the front stitches, and that is important at this stage in the game for me. The first short row of stitches I did, only one or two actually caught the backing!
If I do run out of purple I can look around for a quilting thread the same color, or use a purple coats and clark dual duty, which I know I already have.