The color wheel contains the three primary colors of red, blue and yellow, colors which cannot be broken down into any other colors, and any combination of colors between each range. Colors that contain a mix of two primary colors are called secondary colors, and tertiary colors which is a mix of a primary and a secondary color. You can use the color wheel to pick colors that complement each other, which are colors that are directly opposite each other on the color wheel, and analogous colors, which are any three colors directly side-by-side on the color wheel.
Green is a secondary color which is made by combining the two primary colors, blue and yellow. Green is predominate in nature and growth, health, renewal and environment. Green is also said to represent jealousy, inexperience and envy. Like blue, green is considered a calming color. Green can have either a warming or a cooling effect, depending upon which color it relies most heavily, with yellow being a warm color and blue being a cool color.
The use of green and blue together provides a cool, calm environment, with a distinct prevalence toward nature. Green used with purple presents an atmosphere of high contrast, and is good to liven up a room. The use of green with yellow and black is considered a sporty color, and is often used on products used in the outdoors, such as tents. Green with yellow and orange is fresh and awakening, like a bowl of fresh fruit. Contrasting use of green with red is commonly associated with Christmas colors.
For hundreds of years the color theory has been used by artists, designers, scientists and psychologists to arrange environments or arrangements that go well together and promote certain feelings. Because colors that are not complementary or analogous to each other often clash and can cause mixed feelings and emotions, they are not often used together for just this reason.
The use of color theory has always been abstract, and it really depends upon the beholder as to what emotions are evoked by a combination of colors. Modern art relies more upon the tone of the colors to evoke feelings than the actual color itself.