What makes you decide what guns to paint and what guns not to paint? Maybe you paint all your guns. Or perhaps none at all?
The guns that I don't paint are usually smaller ones with colors that I like. The kind that's fun to just run around the yard with. I'm planning an easy non performance mod for my 240 when I get home.
I just bought this alternate color 240 on ebay:

I'm going to replace the reservoir with the translucent blue reservoir on my current 240:

Then I'm going to sell the other 240 on ebay.
http://hydrowar.com/xp240.html