According to the type of soluble color, compounds and atomic structures, the color in sewage and wastewater treatment and color removal by nano ozone system is practical. True color is created by compounds that absorb visible light.Ozone color removal system is used at the outlet and after chemical and biological treatment, the amount of ozone is determined according to the quality of the outlet waste, temperature and previous processes and used nano ozone system. In case of using the real nano ozone system, the performance of the system shall be increased and the capacity of the ozone generator will be significantly reduced.The quality of color removal depends on the amount of color of waste of the treatment plants, the amount of injected ozone, the ozone distribution system, the type of waste and the temperature of the waste. In order to remove the color of wastewater in different articles, the required ozone is predicted from 50 to 200 mg/liter, which will bring an efficiency of 85 to 90% in color removal.