Water Make-up works just like watercolour paint. If you do not want the colours to mix, be sure to wait for the first layer to dry before applying another colour over it or up against it.
Hint: Regularly change the water you rinse your brushes in and preferably work with two water bowls: one for light and one for dark shades.
General tip: Water Make-up can be used to add (additional) colour to the hair and eyebrows, provided that the hair is not permed, bleached or dyed. Use a toothbrush to do this.