I agree with nabobw -- I use natural colored batts all the time with various colored fabrics -- including mainly white-on-white tops and mainly black backings and they don't show through. The reason to use black batting is, as you mentioned, because of bearding. Bearding isn't actually a problem with most batts anymore because they either are bonded or have a scrim. There are some batts that will beard with looser weave fabrics -- for example, my favorite batting, Warm & Plush, is only needle punched (no scrim, no bond) so with vintage/repro fabrics it will tend to beard some during the quilting process. However, even with W&P, by matching my needle & thread, and finishing by carefully washing the quilt (cold water, gentlest cycle, tumble dry low), I don't have problems after the initial quilting phase because that tiny bit of agitation & heat allow the cotton fibers to swell very slightly and then shrink to close up those holes. Washing/drying on hotter temps will weaken even the highest quality cotton fabric or thread, possibly allowing for bearding.