If I'm unsure what color to pair with another, I usually consult the color wheel. Look for colors across the color wheel form your color (complementary colors) (such as blue - orange, purple - yellow, red - green). Or look at colors on the color wheel that surround your color (analogous colors). And sometimes if that doesn't work, I put my my fabric against a bunch of different fabric at the fabric store and hope I find something that looks good with it.