To dream of coloring a picture in may reflect feelings about trying to bring meaning, love, or happiness an otherwise empty situation. Trying to make a lifeless or empty situation feel good. Trying to give a situation purpose. Trying to “bring something to life.”
Example: A man dreamed of in a lot of pictures. In waking life he had lost his career. He had to find other ways to fill the emptiness of his life until a new career opportunity was available. He created a lot of art and shared it with friends while waiting for a new job opportunity.