Colour vision is the ability to differentiate different wavelengths of electromagnetic radiation. Example- For us the visible spectrum is the portion of the electromagnetic spectrum that is visible to human eye ,(wavelength of radiation -380 -750 nanometres.)We simply call it light. Colour vision depends uopn how a brain perceives lights of different wavelengths.The photo receptors in our eyes gives us ability to detect the presence and intensity of light and allows our brain to create vision of real word. It is not necessary that other animals also see the world in same colours as we humans do, they may have ability to detect wide range of wavelength , and have more photo receptors. Thus they may have more developed colour vision.Technically, color is an illusion created by our brain!