Officially called a "two-color date display", the alternating red and black colors of the date wheel in Rolex Datejust models earned it the popular nickname, "roulette". First seen in 1945, the original roulette date wheel had red numerals for even numbers and black for odd, though this was reversed in some Datejust (Ref. 1162xx) models.
Modern Datejust 36 (Ref. 1162xx) models with black, white, bronze Arabic, and black Arabic concentric dials feature a two-color date display. It can also be installed as an aftermarket modification on other Rolex models using Cal. 3135 or Cal. 3185/3186.