Other than some specific TV shows, and given his age, you will probably have to distill some things. There are lots of things to consider - not just skin color, but eye shape and color, sweath glands, body shape, muscle types, etc.

From general to specific:

A highly theoretical view. But a great read.

http://en.wikipedia.org/wiki/The_Selfish_Gene

More Specific Authors relating to biological and humans. Look through the cited titles for ideas.

http://en.wikipedia.org/wiki/Loren_Eiseley

http://en.wikipedia.org/wiki/Stephen_Jay_Gould

And this classic:

http://www.amazon.com/Naked-Ape-Zoologists-Study-Animal/dp/0385334303

And I have this on my shelf - have not read it yet. It unites many different fields. Inter library loan might be cost effective.

http://www.amazon.com/Human-Evoluti...mp;s=books&qid=1240950357&sr=8-1

For skin color, this study seems to be the last word.

http://en.wikipedia.org/wiki/Human_skin_color

Other:

http://en.wikipedia.org/wiki/Female_body_shape
http://en.wikipedia.org/wiki/Body_shape
http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_073_04.html