Material Wallhack

Just wondering if anyone can possibly give me a resource to where I can maybe see how to actually make a Material wallhack? Just for starters I am looking to make the CT skin Blue, and the T skin red and you'd be able to see it through walls etc, but the walls itself are normal and not transparent.

Im almost certain that it cant be done unless you are using an actual hack and not just changing materials. I understand what you are saying but with the material hack unless the walls are transparent then you cant really wall hack LOL.

I see, well is there any way you or someone else can link me to a tutorial on how to make the walls semi-transparent or?