If you already have photoshop then you can have G2 make the template for you.

Click Aircraft--->select aircraft--->make new scheme
select a name for your scheme and click ok. Real Flight will tell you where the file was stored.

Go in with photoshop and make any editorial changes you wish. And viola a new paint scheme for you plane.

I find that primer gray is the most realistic for me as I have 5 planes that I'm building and none in the air right now

Good luck, and let me know if you need any help with photoshop