Try these websites. You will find them an invaluable resource.
IPMS:
http://ipmsstockholm.org/helpdesk.asp#color_charts
You can go straight to the FS595 (Federal Standard) server which will show you the color or one of the reference charts which will allow you to cross reference several paint manufacturer's numbers to FS numbers. If there is no specific paint match, you can Google the fs number and hopefully someone at some time figured out a recipe using other colors. If all else fails, match your own recipe to the server color (can vary depending on the monitor you are using, etc.). If it's a little off, then weather it heavily!
Another good site:
http://www.fortunecity.com/meltingpot/portland/971/reference/humbrol.htm
Good luck,
PaulR