It's possible that you're seeing the bottom thread (or top thread) through the holes that the needle makes, and those holes will close up when the quilt is washed (or perhaps even when it is taken off the frame and shaken a bit). Before deciding to use thread that isn't really your first choice, examine the stitches carefully. If it's only an occasional peep, I would probably continue with the red and white. If it's really obvious that the bottom thread is coming through to the top, and not being seen through the needle holes, then you can try to improve the tension... or use another thread.