Most people believe they should paint the walls in a dark or windowless room a light color. It seems counter intuitive but just the opposite is true. If there is no natural light, such as in a basement, the best way to treat the walls is to paint them a rich dark color. Without natural light, walls that are painted a light color will simply look lifeless and dingy.
“A light color will never come to life in a dark room but a rich, deep color can make a dim, somber space feel warm and luminous – even though it receives no natural light.” Donald Kaufman
The secret to keep the room from looking like a cave is to use plenty of light or bright colors in the rest of the space. Light furniture, a light carpet, bright artwork and most important, lots and lots of artificial light. Table lamps, floor lamps, and ceiling lights are absolutely essential in a dark windowless room.