There are 36 possible outcomes in roulette, with 0 being the most likely. This means that if you bet on black, there is a 1 in 36 chance you will get black. If you bet on green, there is a 1 in 36 chance you will get green.
Betting on any color has a 1 in 36 chance of winning. On average, each bet has a 1 in 36 chance of winning.