Jeremy,
Not sure what brand paint you have, but the closest match "off the shelf" is from the Testors Model Master line of enamels. you could add white to the colors you alreadt have to approximate the color you need. Add white a drop at a time, stir, then check the color by whipping on a clean white paper towel. Repeat this until you've gotten as close as you can. I provided the photos below of what my eye sees as a very, very close, if not exact match. Therefore, I must admit, I could be wrong. I choose these two colors on your behalf from several photos of the real plane I found on the web. I hope this helps you. Good luck, and go slow at it.
Military Brown and USSR Interior Blue/ Green enamels
Note: the color of the paint in-the-jar will dry darker than what you see here. So I would add white to these for more accuracy.
Greg Williams
Owner/ Manager
Modern Hobbies LLC
Indianapolis, IN.
IPMS #44084