Green is the colour of concentration and intellect. A room decorated in green is very calm and restful and brings elements of nature in. People who like green tend to be cautious and sensitive to detail.
A room that is decorated in one colour is known as a monochromatic colour scheme. This colour scheme is the most expansive in feeling. Monochromatic colour schemes do not have a lot of contrast as you use different values of one colour. Contrast creates energy and makes a room feel smaller. You can also integrate neutral colours such as white, black or gray. The use of neutrals helps your eye to notice different elements in the space.