[Discuss] Texture Hack - Is it possible. topic

I was curious if there a possibility to colour player models, so for example all human characters are red, and zombies are blue, i know there a way to extract texture files from within the game, so is there something you can do so like changing the skin colour to some thing bright so you can visually see a person or make all helmets red etc...

Something like you can do with games such as Counter Strike, just editing the texture which is 100% unbannable.

http://www.youtube.com/watch?v=R2o1ecDQWtk#t=232
Is there a way to colour these models and have the client accept it?