A monochromatic color scheme uses a single color on most every room surface. In this type of scheme, various darker shades, grayer tones, and paler tints of the main color may be included in the palette. In addition, the one color is often paired with white or another neutral.
For example, a monochromatic room in blue might use single shade of blue paired with white. Yet it might also include dark blue upholstery fabric, pale blue walls, medium blue draperies, and a patterned area rug that includes both blue anjd white. The window and door trim as well as the ceiling might be painted in white. (source: About.com)
(images from: FreshHome.com)