While examining the scientific nature of color and the aesthetic considerations of color harmony, we've seen that perception plays a large part in the effective use of color. Beyond the mechanics of perception and the recognition of balanced color palettes lies the intangible, visceral reaction that humans have to color. Colors evoke strong physiological and emotional responses both positive and negative. When you develop your color palette, make sure that the colors you select elicit the appropriate response.

Physiological reactions
Although there has not been a great deal of conclusive evidence linking colors to specific responses, research suggests that certain colors do evoke physical responses. Red, for instance, is a very stimulating color and has been shown to produce increased heart and respiratory rates. Thus, red works as an excellent attention grabber and accent but could easily overstimulate when used as a background color. Similarly, yellow also demands attention, but since it is highly reflective, it creates eye fatigue and aggravation. On the other hand, the color blue has a relaxing effect on the nervous system, and some studies have shown that it increases productivity when used as a background color. However, don't use blue in your color scheme if your product is food-related, as blue is a natural appetite suppressant.

The symbolism of color
The symbolic meaning associated with colors sometimes has precedent in nature. For instance, the color of the sky or the sun creates certain fairly universal associations. However, the underlying meaning that we derive from most colors is based on cultural-specific elements--politics, religion, mythology, and other shared social structures--that may shift over time and across geographical boundaries. Be careful when designing and marketing sites specifically for audiences outside of your cultural reference, since a color that has a positive connotation in one culture may have a negative connotation in another. In addition, most colors have both positive and negative associations. You can emphasize certain meanings over others by using variations of value and saturation, or by using colors that combine two hues.

Common color connotations in Western cultures:

• Red: passion, romance, fire, violence, aggression. Red means stop or signals warning or forbidden actions in many cultures.
• Purple: creativity, mystery, royalty, mysticism, rarity. Purple is associated with death in some cultures.
• Blue: loyalty, security, conservatism, tranquility, coldness, sadness.
• Green: nature, fertility, growth, envy. In North American cultures, green means go, is associated with environmental awareness, and is often linked to fiscal matters.
• Yellow: brightness, illumination, illness, cowardice.
• Black: power, sophistication, contemporary style, death, morbidity, evil.
• White: purity, innocence, cleanliness, truth, peace, coldness, sterility. White is also the color of death in Chinese culture.