Color Theory

Color occurs when light in different wavelengths strikes our eyes. Objects have no color of their own, only the ability to reflect a certain wavelength of light back to our eyes. As you know, color can vary in differing circumstances. For example, grass can appear gray in the morning or evening or bright green at noon. Colors appear different depending on whether you view them under incandescent, florescent or natural sunlight. Colors also change according to their surroundings. You can see this by looking at the color squares below - the reddish outline box is the same color in all the examples.

Hue 

Hue refers to the color itself. Each different hue is a different reflected wavelength of light. White light broken in a prism has seven hues: red, orange, yellow, green, blue, indigo and violet. White light occurs when all the wavelengths are reflected back to your eye, and black light occurs when no light is reflected to your eye. This is the physics of light.

When it comes to using color in art, things get quite messy. Looking at the color wheel above, when using color pigments, the three primary colors used are yellow, blue and red. These three colors are blended together to produce other colors, called secondary colors, such as green, orange and purple. Mix enough colors together, and you get black. Pretty strange, eh?

Computer colors

Computer colors are produced by combining the three colors of red, green and blue together. Believe it or not, you can get yellow by combining these colors (I've never been able to figure out why, but you can!)

Print colors

Things get even dicier on computers when you go to print out these colors. Printing uses the CYMK convention which takes cyan (light blue), yellow, magenta (pinky red) and black inks and tries to recreate the color that your computer created with red, green and blue light. 

Color Value 
Color value refers to the lightness or darkness of the hue. Adding white to a hue produces a high-value color, often called a tint. Adding black to a hue produces a low-value color, often called a shade. 
Intensity 
Intensity, also called chroma or saturation, refers to the brightness of a color. A color is at full intensity when not mixed with black or white - a pure hue. You can change the intensity of a color, making it duller or more neutral by adding gray to the color. You can also change the intensity of a color by adding its complement (this is the color found directly opposite on the traditional color wheel). When changing colors this way, the color produced is called a tone.
When you mix complementary colors together, you produce a dull tone. However, when you put complementary colors side by side, you increase their intensity. This effect is called simultaneous contrast - each color simultaneously intensifies the visual brightness of the other color. 


Harvard refrence;
Bonnie Skaalid. (1999). Elements of Design. Available: http://www.usask.ca/education/coursework/skaalid/theory/cgdt/color.htm. Last accessed 20th Feb 2011.