I recommend starting with his long white hair and pale skin, adding a subtle tint of purples, blues, and whites to really make his complexion stand out. His line markings can be given a dark hue of blues, violets, and grays. His eyes can be colored a deep red and the pupils black. Create contrast by coloring his commemorative headband with bright pinks and oranges and the kanji with a dark shade of blue. His long-sleeved shirt can be colored a dark maroon and the kanji on the back a light gray. His pants should be a deep black and sandals a lighter brown. The markings on his arms can be given a striking contrast of black and white, and his snake tattoo colored with light greens and a hints of blues and yellows. To finish the look, add a silver sheen to his sword. Ultimately, the colors chosen for Orochimaru will create a strong and mysterious look.