I need to paint up a dummy aerial bomb that was made into an ashtray. It is going back to a "real" looking WWII aerial bomb. It is not as big as a 500LB'r so I am guessing it is a 250lb'r.

Where can I find color pics or military manuals with exact bomb markings for the USA?

Dang, that's a challenge all right.

This might become time consuming, but maybe you'll consider contacting some of these folks:

http://www.hardscrabblefarm.com/ww2/

It's a re-enactor's wetdream of a links page.
They have everything BUT bomb markings.

But if there's folks out there who found and recreated everything right down to office forms and even food can labels, then surely one of 'em has just GOT to know your answer.

In the meantime, I'll keep looking when I can.

I found markings for a british bomb but that's it, no american bombs