Changing item color, inventory image

[Damascus]

I'm trying to change the color tint of two entities, the "gameplay/rock_small" and "gameplay/rock_lock_item." All I want to do is give them a purple and yellowish color, that latter of which to give the appearance of gold ore, for example. Yet, I can't seem to do this through the Model or Material Editor, so I don't know how to do this. I also can't find any modeling programs that are free to use if that's what it's going to come to.

I also don't know how to give the rock_lock_item it's own inventory .tga image. I don't how how to make one, for example, and where to put it. Right now it just has a golden circle as it's image and don't know where that image is stored either.