The Multicolor is like a very simple roulette.
The goal is to find the random color.
A number between 00.000 and 99.999 is randomly chosen for every bet with the Provably Fair system.
For every roll of the wheel, you can bet 1 or more colors in order to increase your chances. If you find the right color, the amount of your gain will be the bet amount multiplied by the number of the color: bet amount * color number
If you bet 1 BTC on the color red, and the wheel stops on the red 3, your gain will be: 1 * 3 = 4 BTC.
Here is the table with all the possibilities:
If you are interested on how Automated Betting works for Multicolor, you can check the Dice Automated bet article.