I used 3 colors of paint. I started by painting the whole thing in the medium color (a warm yellow), then used a natural sponge to sponge on a medium blue (sort of a wedgewood color), then finished with a creamy white as an accent and to lighten the whole look. It wore really well and looked like marble until you got up really close. I got many compliments on it from friends and neighbors.
It is important to wet the sponge with water, completely wring it out, then keep it from getting saturated with the color you are applying. It MUST be a natural sea sponge (not a man-made one) or it won't look or work right.
Try pacticing on a something else (I used a flattened cardboard box to get the hang of it and to make sure I liked the color combination). Good luck!