Try to work on your techniques. For solid colored objects you will notice that there are shiny spots and dull spots. That is due to the way light reflects off it. Even for a solid object painted in a single color it does not appear uniform to the eye. You can work a nice effect by putting showdows and highlights to it. Use washes on the seems and other areas where a shadow would be cast and drybrushing for raised areas to simulate the highlights. You can do this by making a wash with black and a little bit of your olive drab, and to highly by using yellow added to your olive drab.
Solid colors don't have to be boring on armour.
The camo scheme I like on the Stuart is the Caunter scheme used in North Africa. It has a base color of light stone though, so that's probably not what you want. But for your next stuart you can apply it. It has a base of light stone, and two disruptive colors of silver grey and slate grey in a straight masked pattern.