BAD used a method I "invented". Basically we made copies of existing clothing items giving them different names. Then we changed the textures on the copies. Back then we had to use a combination of PRP Explorer and good old hex editing. LibPlasma should make this somewhat easier now.
Keep in mind that these are not new clothing items. They still use the same old meshes.
If you don't mind losing an existing clothing item you can "simply" change its textures without making the copy. The textures you replace must have the same DXT compression formats as the originals. For example if you change a DXT5 texture you cannot use DXT1 and vice versa. And if the texture you replace has mipmaps your replacement must have mipmaps as well. PRP Explorer can tell you what kind of texture you are dealing with.
We used the nVidia Photoshop dds plugin to make matching textures. And don't think you are done when you replace one texture. Clothing items often have several layers of textures each with different transparency areas. That is how you can change the colors in one area without affecting the rest.
I remember that once I had figured it out it was just a very tedious job. So I was more than happy when BAD agreed to carry on.
