Is it possible to choose 2 colors and let zbrush do a variation when I paint just with these two colors? when I use colorspray zbrush gives me too many colors.
See color>> http://docs.pixologic.com/reference-guide/stroke/modifiers/
AFAIK, it was supposed to use the foreground and background colors. Always settings somewhere when defaults don’t suit desired results.
I don’t think it’s possible to specify two colors for Color Spray. You might find that the simplest way to get the effect you’re after is to use the Spray stroke and press Alt to alternate between the main color and the secondary color. Setting the Stroke>Flow slider to a low setting will mean you have more control over building up the color.