Every body part of your avatar can have a different skin color.
To find the avatar skin tab, go to
To edit the skin color of the whole avatar, simple change the color next to
Body Parts, as shown below.
Next to each body part there is a color selector that you can change.
Once you have selected the color that you want, press
Next to each body part there is a visibility checkbox.
Unchecking those will make the unchecked body parts invisible.