This cityscape looks like it's from another world. A yellow and green UFO is zooming across the sky and birds take flight as it passes by. The deep blue sky of evening is filled with stars, and the sun is setting over the horizon. To bring out the colors of the UFO, you could start by coloring in the yellow parts with a bold yellow crayon. For the green, use an electric green to make it really stand out against the sky. The surrounding stars can be filled in with silver glitter markers to create a twinkling effect, while the sun could be a vivid orange fading into a yellow as it sets.