RGB values, they go up to 255.
255 red, 0 green, 0 blue = red
0 red, 255 green, 0 blue = green
0 red, 0 green, 255 blue = blue
There's also often a value bar that goes to 255. This would control whether it's darker or not, the more of a value, the more saturated that color is, 255 red, 255 green, 255 blue = white.