Here are a couple of sites that may be of interest::
http:/www.olive-drab.com
Illustrations, color charts, paint numbers, etc.

http:/www.activevr.com
This one has good quality ilustrations with color chips, full color charts for U.S., British and Germans, as well as British armor division formation markings.
Take time to check the other links on both these sites for additional armor, aircraft and naval links.

Art

All I get with the second URL is an advert for a media company.

great sites art, thankyou for posting them
the corrected link is http://www.activevr.com/afv/index.shtml
that should take you directly to the site proper.

kitbasher :-)