Blue shift is also called blue shift, as opposed to red shift. In photochemistry, blue shift also refers informally to photochromic effect. Blue shift means that the frequency of electromagnetic waves (such as light) scattered by objects moving towards the observer moves towards the blue end of the spectral line (meaning that the wavelength decreases). The wavelength shift between mutually moving reference frames is also called Doppler shift or Doppler effect.

1993, Bell Laboratories found that the color of light changed from red to green and then to blue with the decrease of particle size. Some people call the phenomenon that the color of the luminescent band changes from red to green and then to blue or the absorption shifts from long wavelength to short wavelength blue shift.