The ability to change skin color is known in some reptiles, such as the chameleon, but scientists have seen it rarely with snakes and have not yet understood this phenomenon, the group said in a statement.
"I put the reddish-brown snake in a dark bucket," said Mark Auliya, a reptile expert and a consultant for the group. "When I retrieved it a few minutes later, it was almost entirely white."
Reptiles typically change color to camouflage themselves from predators.
The 1.6-foot-long snake was discovered last year in wetlands and swamp forests around the Kapuas River in the Betung Kerihun National Park in the Indonesian part of Borneo island.
"The discovery of the 'chameleon' snake exposes one of nature's best-kept secrets. Its ability to change color has kept it hidden from science until now," said Bambang Supriyanto, a WWF specialist on Borneo.
Scientists named their find the Kapuas Mud Snake, and speculated it might only occur in the Kapuas River drainage system.
The WWF, the international group formerly known as World Wildlife Fund, said 361 animal and plant species have been discovered since 1996 on Borneo, underscoring its unparalleled biological diversity.
But it said that widespread logging has left Borneo with only half of its former forest cover, down from 75 percent in the mid-1980s.
Indonesia and Malaysia have territory on Borneo, which is also home to the sultanate of Brunei.