Any color that contrasts the pure.
Dark blues and greens like Azurite, Raider, Vulcan, and a few others look great.
Another option is dark reds and purples. Vampire, Shaman, Cobra, Magma, Velvet, Demolition, and even elf look really good.
There's also the option of really bright colors. I've seen Toxic and Supernova look really good against a pure relax.