uvmapping alpha channels?

i’m working on a character and found that greybeards lscmuv mapping tutorial helped for texturing, what i want to know is how to set alphas. so i can make the arms a certain color or texture and uv map others.

Do you want to place textures that does not cover all the arm surface? If so, you have to do the following:

When creating your texture make a selection around the exactly area of the detail you want to show and save it as a .tga file. In Blender, when importing the image, select the option “use alpha” in the Texture window (F6) in the image tab. If everything is set up correctly, you will get the arm color covered by the texture only where the selected detail is.

if you need a more detailed explanation, I can post some images.