Interior colors varied from manufacturer to manufacturer and aircraft to aircraft. U.S. aircraft interiors variously used Zinc Chromate Green, Zinc Chromate Yellow, Interior Green, and Dull Dark Green. Depending on how much accuracy matters to you, you may want to do enough research to find the appropriate color for whichever aircraft you're modelling. We do all of those in our Colourcoats enamels, as well as British Interior Grey-Green, German RLM 02, Mitsubishi and Nakajima interior greens for Japanese aircraft, Chamois & Bleu Fonce for French aircraft, and several interior colors for WW2 and modern Russian aircraft.
Cheers,
John Snyder, White Ensign Models, http://WhiteEnsignModels.com