An introduction to why do we see color visible light consists of electromagnetic radiations of wavelength 400-750 nm. Each wavelength is associated with definite energy and produces a characteristic color sensation as it strikes the retina of the human eye. Light possessing all wavelengths in the visible range appears white. The complete absence of these wavelengths causes darkness, black. When a beam of visible light strikes a colored substance, certain wavelengths are absorbed, and others are reflected. Those reflected compose the color of the substance. For example, if a substance absorbs wavelength in the blue-green region of the spectrum, it appears red which is the color of the remaining wavelengths. On the contrary, if the red light is absorbed with complementary colors observed.