GT3 is a really old but also really cool server / client mod that enables an extra team (yellow) in team based gametypes. Extract the gt3 folder to your sof2 root directory, the same as you would any other mod like RoCmod or OSP. Install Guide : https://www.sof2.org/mods/
This mod is very nice, is a texture mod with the addition of sound steps, weapons sounds,glow skin and i wrote the code for a shader to have a glow gold rotating Shotgun and a white rotating ak! Teo’s Mod v.4 from Teo on Vimeo.
This mod is very small, includes only the essential like laser, glows and some sound.
Mods: Place the .pk3 file in your base/mp folder (be sure that there are no other mods in it). Then just run SoF2