I just do not think that it is a good idea. Paint will certainly chip, show wear marks, etc. You need a hard surface that will show no marks. Stick with the plastic formulations, or even one of the stone base materials. Never think about painting for changing color!
It is not a good idea to paint kitchen countertops. The kitchen counter is the most used work surface around most houses. Because of this it needs to be durable and able to withstand a lot of wear and tear. Formica is an inexpensive, much more durable alternative.
DO NOT paint your kitchen countertops. The paint will peel and chip and look awful in just a few days. You would have better luck laying tile over them.