Examine your color wheel and notice that the colors red, yellow and blue are equidistant from each other. These are called the primary colors, because they cannot be created from other colors, but from these three, you can create all other colors.
Notice that between the primary colors are orange, purple and green. These secondary colors are made from mixing the primary colors that flank them. Purple is made from red and blue, green from yellow and blue, and orange from red and yellow. Similarly, all the colors of the spectrum are made from mixing these primary and secondary colors.
Look at the colors directly across from each other on the color wheel, for example blue and orange. These are called complementary colors, because when mixed they cancel each other out, resulting in gray. Other common complimentary pairs are green/red and yellow/purple. Because complement are opposites, they have strong impacts when combined.
Consider the color wheel again. The color yellow is lighter in shade than blue, for example. In addition to hue, each color has a value, corresponding to how light or dark it is. Yellow has a naturally lighter value than blue. To make any color a higher value, add white; to make a color a lower value, add black.
Compare primary and secondary colors on the color wheel to colors around you. The colors on the color wheel are much brighter and more intense than most of the colors in the environment, which are usually duller or more neutral, because most colors are not fully saturated like the colors on the wheel. The degree to which a color is saturated is called its intensity. The three qualities--hue, value and intensity--are used to describe and analyze color.
Expand your knowledge of color theory by enrolling in a course a local school or college, or referring to online courses. There are two online resources listed below.