White isn't transparent, transparent is transparent.
Textures are encoded into the .tga format which supports red, green, blue and alpha channels (RGBA). The alpha channel is where transparency is encoded.
If you want to have transparent textures (which are legal, I used them for years and years over 5 years) then you need to make a texture using a program like Photoshop or GIMP (mspaint can't do it) and make it completely transparent.
To answer your question though, yes you can have white textures.
you cant half half white force-half elf force. to get elf and white on the same joint, you would have to buy the joint textures.
also regarding the transparency, the body part has to be defined. Clearly defined. you can have a single dot, for example.