Analogous colors are near each other on the color wheel. In the photos above the blues, blue/greens and greens used are analogous colors. They produce a harmonious, rich, monochromatic look.
Below, the same room is shown in complementary colors (red and green), which are opposites on the color wheel. They look bright when placed next to each other, and may produce a more lively look.
To influence the feel of a room, keep in mind the affect different color schemes will have.