The following information can be used from both an artistic and marketing point of view.
In traditional color theory the primary colors; red, blue and yellow are the three color pigments that cannot be formed by any other combination of colors. They are very visually strong colors and when they are used together their contrast can create a sense of urgency, which is why they are often used as colours for superheroes costumes and fast food chains.
The secondary colors; green, orange and purple are formed from mixing the primary colors.
Yellow-orange, red-orange, red-purple, blue-purple, blue-green and yellow-green are the tertiary colors and are formed by mixing a primary and a secondary color.
Color harmony is when colors are placed near each other in a manner that is pleasing to the eye. 'It engages the viewer and it creates an inner sense of order, a balance in the visual experience'. When an image is not harmonious it can be very displeasing to the viewer.
Color Harmony Formulas:
"Analogous colors are any three colors, which are side-by-side on a 12 part color wheel, such as yellow-green, yellow, and yellow-orange. Usually one of the three colors predominates."
Complementary colors are any two colors directly opposite each other on the color wheel. These colors are very contrasting to each other.
What Colors Mean
Red: Red is a very visually strong color and is usually associated with blood and fire, which sometimes implies violence, danger or power. It is also associated with love lust and passion. Variations of red such as pink or light red suggest femininity, sensitivity, love and friendship
Yellow: Yellow is known to represent warmth, joy, intellect and energy. Many people would associate it with spring and it is known to give a sense of refreshment. Scientific tests have shown that yellow stimulates mental activity. In some cultures yellow represents cowardice; thus the term 'yellow bellied'. Yellow also represents citrus fruits and other healthy food.
Pale yellow can sometimes denote sickness and decay.
Orange: Orange is also associated with warmth but not with the aggressiveness that red implies. It represents enthusiasm, creativity, determination and success. Orange apparently increases oxygen supply to the brain, which produces an invigorating effect, and stimulates mental activity.
Orange is very eye-catching which makes it very successful in advertising. Like yellow, orange is associated with citrus fruits and healthy eating.
Green: Green is traditionally associated with nature and growth, freshness and fertility; it is also shown to suggest a feeling of safety, it is also traditionally found on medical products. It can also imply innocence or lack of experience. Dark green is traditionally associated with money and finance; and sometimes with greed and jealousy, thus the well-known phrase 'green with envy'
Blue: Blue often symbolizes depth, stability, loyalty and faith. Blue has a very calming effect on the mind and the body; it slows down human metabolism to produce a calming effect. Blue is the traditional color of water and sky and is often successfully used to advertise services related to purity or cleanliness. Blue is also known to suppress appetite; it is also traditionally a very masculine color.
Purple: "Purple combines the stability of blue and the energy of red." Purple is associated with royalty, power and wealth. It is rarely found in nature, some even considering it to be an artificial color; during the Middle Ages dyed clothes were a luxury afforded, and purple could only be made by combining red and blue dyes and was usually worn by the royalty as a sign of wealth.
Purple is also associated with youth and surveys show that it is the most appealing color to children with light purple is considered to be a very feminine color.
White: White is associated with simplicity, innocence, purity, goodness peace and perfection. Religious groups regularly use it as a symbol of faith. White is traditionally associated with cleanliness because it can show up any dirt or imperfections quiet easily, which is why rooms in hospitals or any other environment considered to be sterile white. It is also frequently used to promote technological products to imply simplicity e.g. Apple.
Black: Black represents death, mystery, evil and formality. Black has always been seen as a stylish, yet sometimes formal and elegant color. It can also show authority, but is usually associated with evil and badness; the opposite of white. Using black as the main color in an image can give it a very dark, gloomy and sometimes ominous atmosphere.
Grey: Grey is considered to be a boring color as it is not very visually stimulating and is associated with decay old age, neglect ion and sadness.
Color Categories And Their Use
Colors can generally be grouped into two categories:
Red, orange and yellow
Blue, green and purple
The famous color theorist, Georges Seurat believed that the direction that colors were running in also had an impact on the viewer's response; he believed that warm colors going upwards had a light, happy effect, that cool colors had a sad, dull effect and that mid-tone colors (e.g. beige and other muted, pastel colors) going horizontal had a calming effect.
Seurat also discovered that the halo effect created by looking away from a bright object is always made of the object's complimentary color; e.g. looking at a bright blue light would cause a red halo effect in your vision afterwards.