Might the ones you saw that were light have been weathered?  One popular weathering trick is to add a light colored overcoat or wash to represent paint chalking.

Make your own. Mix in some yellow or white with your olive drab and add some fading with the airbrush.

Lots of variations in OD,here is a good article on OD

www.militarymodelling.com/.../4536

That article posted by Tojo there is a fantastic resource.

You've got two issues here, some people lighten the paint as you go down to smaller scales with a set formula - personally I just screw with it till it looks 'right'. Still it probably should be somewhat lighter on a 1/72nd vehicle. Two, the paint does fade as it weathers in the sunlight.

Frankly I'm not sure how much you can do if you're using a spray can though since you're kinda stuck with what they package.

This is where you run in to "scale effect". That color looks perfectly fine on a 1/35 scale tank, but on a 1/72 kit, it does appear much darker, even though in actuality it is not. Since you have used a spray can, you can not alter the color at all as suggested here. But you can apply top coats that will lighten the base color as they add up and dry.

If you are using a spray can, then do a filter of dark yellow to lighten the shade. Easy enough with an air brush as it can be custom mixed to a lighter color.

Good day, thanks for the replies. I guess I'm gonna try the weathering first since it is still in base color. I may no longer be able to achieve the "greeny" color but at least maybe I'll still be able to achieve the faded olive drab effect as shown on the article posted by Tojo72. I'll post my little sherman here when I finally have if completed. Thanks! : )