I have a document of unknown origin, in fact I had to retrieve it from the garbage, that has the following formula for USN Interior Green.
XF3 - Flat Yellow (2 parts) + XF5 - Flat Green (1 part).
Here's a link to a Tamiya paint chart - http://www.ipmsstockholm.org/colorcharts/stuff_eng_colorcharts_tamiya.htm