Huygens’ principle, in optics, a statement that all points of a wave front of light in a vacuum or transparent medium may be regarded as new sources of wavelets that expand in every direction at a rate depending on their velocities. Proposed by the Dutch mathematician, physicist, and astronomer, Christiaan Huygens, in 1690, it is a powerful method for studying various optical phenomena.
Huygens' principle, although very important, only holds true if there is no rotation, so as long as the outward pressure is uniform. That is why Huygens never explained the formation of colors. Color formation involves rotation and deformation of spherical bodies, so that the geometry moves from radial to bi-lateral, in order for radiation and transverse waves/colors to become visible.