You know how your favorite color looks, but have you ever thought about how it makes you feel?

Colors can affect your emotions. For example, it is generally accepted that red makes people feel agitated, even if they are not fully aware of it.

"Bright colors are very stimulating, and muted colors are very soothing," said Jill Morton, a color expert based in Honolulu who has worked with major companies to come up with colors for their products.

Morton said that one reason colors might affect us is that over thousands of years, humans have learned to respond to colors based on their roles in nature. Green, for instance, might make people feel fresh and hopeful because it is associated with healthy crops and abundant food. Likewise, red might represent aggression and fear because of its association with fire and blood.

Today, colors are used in marketing to try to get people to react a certain way. For example, Morton chose the colors for a new kind of pain medicine for adults. The company wanted to stress how quickly the medicine works, so Morton made the tablets red (to suggest something fast) and gray (something high-tech).

There was a controversy two years ago when a college football team in Iowa painted the visitors' locker room pink. Pink is supposed to be a calming color, so the thought was it might make the visiting team less aggressive on the field.

Some people don't believe in these reactions, but there are studies to support them. One showed that Olympic athletes who wore red uniforms won their competitions slightly more often than those who wore other colors.

Some basic theories about the psychology of colors or the emotional reactions they stir:

RED

Causes the heart to beat faster.

How it can make you feel: Agitated and jumpy, rushed, hungry, fearful, strong, passionate.

Cues in nature: Red meat, blood, fire, berries.

How red is used: To show energy, strength and speed (examples: race cars and fire engines). Red is often found on the walls of fast-food restaurants because it makes you hungry. It also makes you eat more quickly.

BLUE

Recedes, so objects appear farther away.

How it can make you feel: Content, clean, tranquil, spiritual, trusting, depressed.

Cues in nature: The sky, oceans and lakes, blueberries and fish. Also mold and bruises.

How blue is used: It's the most common paint color for bedrooms; also, police uniforms. Blue suits suggest loyalty.

GREEN

The most restful color to the eye.

How it can make you feel: Fresh, hopeful, young, lucky, peaceful.

Cues in nature: Plants, grass and trees; some lakes, rivers and shallow ocean areas.

How green is used: Popular for home decorating. Also helps people feel calm in schools, hospitals and rooms where people prepare to go on television.

YELLOW

The most visible color of the spectrum; the eye notices yellow first.

How it can make you feel: Cheerful, hopeful, excited, focused.

Cues in nature: The sun, fruits and vegetables, flowers, autumn leaves.

How yellow is used: To get attention; on emergency vehicles, road signs and taxis. Keeps you alert and concentrating, so it's a popular color for writing paper. Can be overwhelming to the eye, so it's used little in fashion.