There are three primary colors - red, yellow and blue. Combinations of these three colors produce three secondary colors: purple (red and blue), green (blue and yellow) and orange (yellow and red). Further mixing of these colors can produce a whole range of tertiary colors from which to compose your photographs.
Usually, these colors are arranged in what is known as a color wheel which can be seen below.
Here is a video on the subject of color theory in photography:
Color & Perspective
Color Tinting & Shading In Photography
Color Psychology In Photography
Color Balance and Highlight