Everything I have seen on US arctic camouflage patterns in the modern era has just been plain white. Uniforms used to have black looking splotches mainly because they were copied from older German uniforms. Modern uniforms and arctic covers are just plain white. Camo netting and such are also plain white these days.
For interesting winter or tundra camo patterns, check out a Jane's manual on armor and look at some of the Soviet and Russian pieces. They have a very nice pattern that uses a dark forest green, grey, and light grey that is really cool looking.