Different wavelengths carry different amounts of energy per light particle ("photon"), with blue being more energetic and red less. However, the total power output of a beam of light is equal to the amount of energy per photon *times* the *number* of photons, so it is quite possible for a red laser to be more powerful than a blue one, for example.

Different substances also reflect or absorb different wavelengths. This is due to the spacing and energies that bind the atoms together; wavelengths at critical energies that excite atoms in the substances will be absorbed, and different substances are, well, different.