That just means that he sent it to an anodizer (consider it someone who "paints" guns different colors... The process is the farthest thing possible form painting through. It's more like dyeing the metal with an electrically charged pigment.) and picked some colors from a palette and had the anodizer change the colors of the gun to that.
Doesn't change the performance of the gun (although a ****ty anodizing job can lead to poor tolerances and a gun in worse condition that it was in before. Uncommon, but happens.) to be anything better. Usually it's only done to expedite a sale where money is needed but not as massive of an issue.