To be honest, if you're coloring the picture like you are, the sun should not be where it is. When the sun is that low in the sky, colors change. Admittedly, you can change the colors later, but you've drawn it thus far with a mid-day sun. Also, even if the sun were where it is, it's millions of miles away. All of the figures in your picture should be lit from behind, but you've shaded as though the sun were a lamp sitting between the people and the tree. Shading and nitpicky flaws are also present, but those can be addressed when the picture has some basic shapes solidly defined properly.