What is the main difference between mechanical and electromagnetic waves

Although green light has a lower frequency than the blue light, but green light has the longer wavelength than the wavelength of blue light. The wavelength of green light is longer by a small margin than the wavelength of the blue light. Red light has the highest wavelength among all the available colors of light. Any color of light is nothing but an electromagnetic wave that enables us to see things around us. Humans mostly can see wavelengths between the Electromagnetic spectrum and the Ultra violet region.