Green laser pointers is now the world's most popular laser pointers, because the green light than red light 6 times more than red light beam significantly, while the price is much cheaper than the blue and yellow.
Green pen is the wavelength of light emitted 500-550nm, the wavelength sensitivity of the coefficient table, as is the closest one wavelength. Green is undoubtedly efficient light source, the eye more easily identified. The green light sensitivity of the human eye is higher than a lot of red; the other is green light scattering in the atmosphere more than red light.