What are the differences between the 3 versions of metalduct001a?

[The Tiny Desk Engineer]

They look identical in the texture browser, and so far I haven't heard anyone say anything mentioning any differences. I also can't find anything about the textures on the internet. Do they have any visual difference at all in-game, and should I ever use any of them instead of the regular metalduct001a?

 

[worMatty]

If you mean Props/metalduct001a_red and _blue, the former's environment map (cubemap) is tinted red, and the latter's is tinted blue.

You can inspect materials by opening tf2_misc_dir.vpk using GCFSCape. The game also mounts the VPKs in the Team Fortress 2/hl2 dir. The Source SDK wiki will tell you about material properties.