I would like to point out that Orange is acting exactly has he typically does when he is scum. Posts a lot, taking control of the conversation, making his reads on everybody, but no case is any stronger than "pies."
Yeah you can change textures by opening the corresponding DDS file or making a new one as long as it has the same name and is placed in your game's data directory. Keep in mind there is blue lighting around the PTs, so even if you change the PT color, things around it will still light up blue.
I remember getting that error a long time ago, and I remember fixing it, but I don't remember how. Which OS is your laptop on? 7? I guess the most basic question would be whether you have the proper w3d mapping plugins in the plugins folder? Another thing is to see if you need to install the directx redistributable from Nov 2008. Do you recall installing anything like this?