This Necrozma is quite mysterious. Its small, dark body is offset by its bright, white head. It has two large, glowing red eyes and a long, ghostly white tail. Necrozma is a rare and incredibly powerful pokemon, believed to be able to rule over the sun and the moon. If I was to color this picture, I would choose a dark, shadowy color for its body, like a deep shade of blue or purple. Its head could be a bright light blue, or a shimmery silver. Highlighting its eyes with a deep red would make it truly stand out. I would likely use a pale white to add depth to its tail, to help it look truly ghostly.