OD paints for different genre

I don't do that much armor, but picked up an anti-tank gun yesterday.  In looking at documentation colors I am reminded of something I have wondered about previously. It seems to me that OD painted aircraft look like a different color than OD armor, vehicles, and ordnance.  The aircraft look more brownish.  Or, to say it another way, armor and stuff seems to loom more greenish. Is there indeed a different color for OD for aircraft than for ground stuff?