I would start by coloring the sky with a gradient of dark blues, from almost black to a lighter navy. The sun can be colored a gradient of oranges, from a deep shade, to a brighter one around the white dot in the center. The planes should be colored with a matte black tone, and the wings with a glossy dark blue. I would add some shadows and highlights to the planes to give the illusion of a 3D effect. The sun would be finished off with a bright white outline and some highlights. Finally, I would add a few highlights and shadows to the ground, to give it a more dimensional look.