My pistol is blue and purple when I look at it in inventory but when I equip it its green? it seems a few gun colours don't match the image in your inventory. it's a little annoying because it would have matched my characters looks, but it's green?
It often the case
In the inventory, it's mostly a "generic" picture and never really represent the gun's colour in real. The only ones that are 100% faithful are for iconic weapons.
(in short, there are fewer weapon images for the inventory than possible colors in the game)