Usually, these pointing devices emit a unique indigo blue light with a wavelength between 360 and 480 nanometers, although most of them emit 400 nanometer beams. The light pen with a wavelength of about 405 nanometers is actually no longer pure blue, but purple. However, some people can easily confuse pointers that emit blue or purple laser pointer because the two types look very similar.
See more:red laser pointers
