Well now.
A paint job isn't so easy as say doing it on something random you have around your house. Its possible to just go at it with modle car paint or something but the quality and just long lasting effect.
A true 'paint job' on a paintball marker would be called annodizing.
There are tons of places who do high quality anno work. What they do is strengthen the metal and adding color to it. That way if you are to take a hard dive the color doesn't scratch away...it simply scratchs.
I personally get my gear annoed by pbcustomz.com jermey does amazing work and worked under some of the best annodizing companies out.
The problem is this will cost you over 100 bucks for a solid anno. Ive seen jobs done for over 500 bucks and they are amazing.
A custom color will add personality to your gun and cost you about the same as a good upgrade. In the end your resale will go up slightly. Unless you are planing on keeping the gun for a while it really isn't worth doing on a medium end gun.
when coloring a gun its good to keep it origonal. don't do the same old pink or just flat block color. be origonal do something new and have fun with it.