What would a casino without a roulette wheel? That game is so elegant, red and black has become synonymous with online gambling, the greatest attraction of online casinos and real casinos. No doubt, online roulette is still the quintessential casino game. The wheel is a series of compartments numbered between 0 and 36, combining the colors red and black. American roulette has two green compartments, zero and double zero. Whereas European wheel, has a single green for the simple zero.