How do you set a specific portion of a source engine model to be colorable?

[TheMrFailz]

There's a lot of models on the workshop for Gmod that have it set up so that when you set the model's color, it only colors a small portion of the model (for example, the paint on a car). I'm trying to recreate that but I'm not sure what I should be doing in my QC file.

(basically, is there a $ flag or something I should be using?)

[dlight]

I dunno how gmod does it, but maybe check the materials of those meshes. They may some $blendtint+ parameters.

[TheDaveSecond]

https://developer.valvesoftware.com/wiki/$blendtintbybasealpha

Make an alpha channel for your VTF for where you want the model to be colored, the more transparent a part of the texture is, the less it's colored.
Then add these to your VMT:

"$blendtintbybasealpha" "1"