I like this idea, it's very cute. As far as color, the only thing I would do is warm up the skin on the soldier. Doing this will make my eye travel from the little girl, which is very warm compared to the background, to the soldier who is also surrounded by the cool green background. Other than that, nice one :)

I like your drawing a lot, although I would add some more white highlight areas maybe on the tank. The sky should be lighter than the ground I think too.

Hi Liandro! I love the picture and the moment it captures. "I don't care where you drive that tank of yours, but it wont be across this flower, I won't permit it!" :D It's so sweet, and so relevant. The theme touches me. So it's the greens and reds that are challenging for you? If so, very corageous to make this piece with just those colours. And well done. I'm definitely no professional, but with my eyes... I might emphasize the root of the flower with a darker value, or, alternatively, give some highlight to it, just to have the focus of a viewer on what's going on in this scene, why is she stopping a tank? Same with the sky / clouds, some variation with values or some shading could give the picture a more striking atmosphere. I like it that you've chosen to use green on the soldier and red for the girl, since red reads more powerful or, in this picture, authorative, so it's an awesome contrast: a common girl with a stop sign has more power than a soldier sitting in a tank :D. Overall, I think you have here a great colour scheme, wouldn't change a thing if not emphasize with darker values or highlight what you most want to show.