Need help making colorable VTFs

[TurctheGamingDragon]

I'm currently working on making some materials for a model I'm working on colorable, but I don't know how to do it. I tried doing some Google searches and even searched here on the Steam forums, but found nothing useful from either.
So to anyone who's made colorable VTF files before, how can i do it?

P.S: for those wondering, I use GIMP to edit materials and Notepad++ to edit VMT files.
P.PS: I tried asking this same question over on the Garry's Mod forums, but nobody responded so I thought I'd ask for help here.