A monochromatic color scheme consists of varying shades in one hue. Imagine a strip of paint colors and how the shades vary on one strip -- these shades are monochromatic.
A one-color scheme room is far from boring when you add a range of intensities. Create a base with a wall color and use large furniture to ground the base color. To keep a monochromatic palette interesting, add patterns and textures. This could mean glossy lamps, embroidered, textured and patterned pillows in a variety of hues. This gives the eye a break from solid color.
To create more places for the eye to rest, use neutrals. This will tie everything in the room together. With plenty of texture and pattern, and a combination of color intensities, a monochromatic color scheme plays out vibrantly all while relying on a single color.