Hypomelanistic, it's a Codominant trait the reduces black pigment. In boas it usually makes them appear redder. It's the same gene as any other hypo boa, but the different localities express differently.
Vin Russo, the owner of the site that was just linked has a great picture showing Panamanian, Nicaraguan and Colombian hypos, but I can't find it right now.
Nics are fun, although of of my hypo females is pure evil.