It’s not just colleges. Look at recruitment brochures that businesses put out - the people pictured tend to be young (with possibly a token older “mentor” type, usually an ethnic minority or woman - or both) and a mix of non-whites and females.
The Office- Diversity Day
http://www.youtube.com/watch?v=HK-Cf9R4q-c
http://www.youtube.com/watch?v=PopWnOuuqO8
http://www.youtube.com/watch?v=idNDrOUWVwQ