The generally accepted number of colors of the rainbow is seven, although the rainbow has only six colors to many people, and others claim that the number of colors is infinite. Sir Isaac Newton used prisms to break down white light into the visible color spectrum.
Newton originally divided the spectrum into five colors but added two more to form the seven-color basis used today. These colors are red, orange, yellow, green, blue, indigo and violet. These colors fall with the 390 to 700 nanometer range of wavelengths that most humans can discern. Some people fail to distinguish between blue and indigo and insist that the rainbow contains only six colors. Others claim that there is an infinite number of colors within and outside the visible spectrum. For example, the infrared and ultraviolet components of sunlight have wavelengths that humans cannot detect with the naked eye.