Abstract 10.1002/zoo.1430130106.abs Green tree pythons, Chondropython viridis, are polymorphic for color as juveniles, commonly being primarily yellow or brown until becoming mostly green at about 1 year of age. We tested the hypothesis that the different morphs arose as a result of selection for differential background matching, yellow morphs selecting light-colored backgrounds, and brown morphs selecting dark-colored backgrounds. Twelve yellow and eight brown morphs were placed repeatedly in individual testing enclosures and allowed to choose between black and white or yellow and brown halves of a t-perch. Trials showed that both color morphs preferred dark over light perches. We tentatively suggest that individuals chose dark-colored perches for purposes of concealment. © 1994 Wiley-Liss, Inc.