Kai and Gerda are both children pictured in the coloring page, each with blonde hair, standing next to each other looking out a window. Kai is standing on a chair and has one hand on the window sill. For Kai, I would choose to color him in a deep blue shirt with a light tan pair of pants. His hair could be an ashy blonde. As for Gerda, she could have an off white dress and sandals, with her hair a brighter shade of blonde. To give a little bit of contrast, I would choose a deep green color with yellow flecks for the window sill and a light blue to represent the wall behind them. The sky outside the window could be a vibrant blue with white and yellow clouds. And to add a subtle bit of sparkle, I would sprinkle some gold stars in the night sky.