Secondary colors are colors that are a result of two primary colors mixed. However, there are different primary colors for light and pigment. The primary colors for light are red, green, and blue (not to be confused with pigment primary colors: red, yellow, green). Do not forget that mixing colors with light is very different than with pigments. While red and green would equal brown in pigment, red and green would equal yellow in light. Here is a list of secondary colors and their origins:
red + blue = magenta
red + green = yellow
blue + green = cyan