SBG, Any color, preferably a pastel one, rather than a strong color, because a lot of our scrappy prints are strong colors. :-) White is fine too though. White is well-liked, is predictable, it seems everybody uses it, and has it.
But I do like the idea of florals that was mentioned. Maybe a floral with any solid color, or fabric that reads as solid (like some tone on tones or blenders)? I think using florals where the flowers are the size of a dime or bigger would be more attractive with a solid paired with a tiny calico print.