Eliza and The Moonchild — Emma Chichester Clark

A small moonchild tires of his white moon surroundings and whizzes down to earth only to find it a shadow-dark place without color. He meets Eliza, who reassures him that the morning will bring color, and together they watch the sun rise while the little girl paints all they see. The moonchild returns home with their picture and a paintbox of his own that he uses to bring color to his world.