The color we see comes from our sun and from light bulbs. Our sun gives off light that lights up our world during the day and indirectly lights us at night as a reflection off the moon. The moon may seem to be shining on us like a flashlight but really we are only seeing sunlight bouncing off the moon. Light from the sun includes all colors of the spectrum (See picture below) and when every color is present, the light appears white. The absence of all color appears as the color black to the eye. As we all know, when there is no light it is dark.
We see color several ways. We see color from lights and colors that are reflected back to our eye from two-dimensional and three-dimensional surfaces. The interesting thing about surfaces is that they soak up colors differently. The surfaces of apples suck in all light except for the color red. This color is reflected out and is seen by our eyes. Have you noticed that colors are duller at sunset? This is because much less light from the sun is there and being reflected by surfaces.
Once the colored light reaches the eye, the eye sends a signal to our brains through our nerves and our wonderful brains make sense out of the color. Our eyes are also wonderful machines. There is a hole in the front of them called a pupil. The pupil closes or opens depending on how much light there is. In bright light, the pupil closes to keep it from getting too bright and hurting our eyes. When the light goes inside our eyes it goes through a lens just like the lenses on glasses you or your friends wear. The light goes through this lens and hits the back of the eye called the retina. The retina has lots of sensors called rods and cones. The cones then send a signal to the brain about what it sees.
Eye cones are special machines too. They are made to see three different colors: red, green, and blue. When the color blue goes into the eye, the blue cone tells the brain, "Hey, that color is blue." Because we have only three different colors of cones, we aren't able to see all colors. Ultraviolet light is a color that isn't able to be seen, for example. Some animals and insects have more cones and can see colors that we can't see. People who are color blind have damaged or missing cones.
How well do you see color? Did you know that only one out of 12 men see color correctly while one out of 255 women see color correctly?  You can test yourself by visiting the Online Color Challenge.
Colour from lights
As I said earlier, we see colors two ways- from lights or from reflections off objects. When you have a light bulb that is red, it makes everything look red. Photographers who make prints have to make them in "dark-rooms." Dark-rooms had red lights in them called infra-red lights. Red will not ruin photo paper or film because it is made not to be sensitive to the color red. Another way we see colors from lights is from televisions, and overhead projectors. Televisions actually only shine three different colors- red, green, and blue- just like the cones of our eyes. When more red lights are lit, the colors on the TV or overhead appear reddish. When more green lights are lit, colors appear greenish. Depending on how many other colors are lit, the green light can be seen as yellow.
Color from surfaces
Color is very important to artists who create things in color. As I said earlier, the colors we see from surfaces are actually colors that are reflected off an object. Each surface and object soaks up different colors. This includes paint and ink. Paint and ink soak up different colors too. Red paint soaks up all colors except for red. The color red then bounces off the paint and goes to our eyes. Ink that is printed on paper also soaks up different colors. People who think they know how things soak up colors will use big words like atomic vibrations and rotations, molecular orbitals, ligand-field effects, and charge transfer.
Most of us study color by looking at Color Wheels. Color wheels have all the colors go around in a circle. The simplest color wheel shows three colors: red, yellow and blue. We call these primary colors because depending on how much of each color is mixed, we can mix all colors with them. Most elementary students who play with mixing colors usually end up with the color brown. This is because when you mix these three colors together, you get the color brown. They end up with brown because they don't clean their paint brush well or they mix the colors too much.
When you mix two primary colors, you get secondary colors. When you mix red and blue, you get the color purple (violet). When you mix red and yellow you get orange. When you mix blue and yellow you get green. Purple, orange, and green are secondary colors. When you add one color to secondary colors you get tertiary colors. Yellow-orange and blue-green are tertiary colors. Colors on the opposite side of the color wheel are called complimentary color. The complimentary of green is red. The complimentary color of blue is orange. You can see them in the color wheel below. They call them complimentary colours because they compliment each other. Complimentary colors look good together.
Tint, Shades, Value, Saturation, Tone, and Intensity
Tint is the lightness of a color. You can make color a lighter tint by adding the color white or if you are painting in watercolor, use more water. If you add the color black to a color, you make it a darker shade. So when you lighten a color change its tint. When you darken a color you change its shade. The lightness or darkness of a color is called a value. Intensity is the brightness or saturation of a color. A color is more intense when it is a pure color and not mixed with white or black. When you mix a color on the opposite side of the color wheel to your color you change its tone. Jay Johansen is an artist who uses colors with more intensity.
Books about color
Understanding Color: An Introduction for Designers - Understanding Color, Third Edition is an authoritative source of information and practical solutions for students and professionals in graphic design, architecture, interior design, landscape architecture, and industrial and textile design.
Color Design Workbook: A Real World Guide to Using Color in Graphic Design - From the meanings behind colors to working with color in presentations, this book provides readers with the information needed to apply color creatively and effectively to their design work. The science behind color theory is explained in easily understood language, and case studies are included to show the effects some color choices had on both their clients and consumers.
Video that helps with memorization of the color spectrum.
Color in Motion Animated - Interactive experience of color communication and symbolism by Claudia Cortés.