I ended up looking for answers to this very question the first time I did some actual piecing and realized there was no way I could match all the colors. The links I found all suggested black, white, beige or grey, and I find one of these neutral colors usually works pretty well.
Occasionally, if I am able to find a color that works better, I will use that instead. For instance, when I made my ballerina quilt, I found that Gutermann had a soft mauve that blended really well with both the pinks and the purples in my fabrics.