Hi - Generally the color scheme for a mk.I or II is Dark Green on the top and sky blue on the bottom. If you want to camouflage it, use a comb of the drak green and dark earth. I recently completed a 1/32 spitfire mk.I and instead of the dark green, I used Olive Drab. I just think it looks better and more "military". The dark green sometimes looks a little to bright for me. When you gloss the olive drab, it looks great - like a dark, deep green. But that's my preference.
Check out the link below: you'll see the color scheme I described above - third picture down(dark green & dark earth). The pictures below that, you'll notice the green is a bit darker, that's sort of what the olive drab looks like on mine that I just did (I used model master olive drab).
http://www.aviation-history.com/supermarine/spitfire.html
Hope this helps.
Regards,
Paul