Uh honestly I don't know what the heck "colorshiftable" means! I don't know how to script and no one's really shown too much interest in putting my models in-game so I haven't bothered learning the technobabble.
Colorshift is when a part of the model uses the blank.png texture and in the .cs file for the weapon, there is a part of it's script that is
colorShiftColor = "0.5 0.5 0.5 1.000";
This determines the color of the parts of the model that uses blank.png (or any texture that is transparent), it goes by RGBA, red, green, blue and alpha, alpha being what controls the transparency, correct me if i'm wrong