If you want to paint new uniform textures you have to create new texture tga files.
you can find the original ones in data/models/characters/bodies/BodyFemS and BodyMaleM
You should use Photoshop to create a new document 72 dpi 512x512 pixels in size - open an old uniform texture file and look at the texture positions - I recommend importing the old uniforms and paste them into a new layer and set the transparency of that layer to 40 or 50 percent.
You can hide that layer later if needed but it makes a good template and it?s good for orientation.
If you want to know more just ask
good luck