I am playing with green color and I get darker spots. Paint is very well mixed, and I had this issue only with green color. It's pure paint ,no reducer, 0.5 and 20 psi. I suspect this is spitting of paint, the part which I don't understand is that those spots are darker then the object when it's fully saturated with paint. So is this cause of paint build up on needle and then airbrush just spits it?