The phenomenon by which the extinction of blue light by interstellar matter is greater than the extinction of red light so that the redder part of the continuous spectrum is enhanced.
A change in the color of an object, caused by selective absorption of its light by material lying between it and the observer, in which shorter wavelengths are more affected than longer wavelengths. As in the reddening of the light of the Sun and Moon when they are near the horizon, by our atmosphere, or the reddening of the light of distant objects by clouds of interstellar gas and dust.
the preferential scattering of the shorter wavelengths of light as it passes through a dust cloud, so that a large fraction of the bluer wavelengths of light are scattered away from your line of sight while a large fraction of the redder wavelengths of light make it through the dust cloud unaffected. Dust clouds in space make stars behind the dust clouds appear redder than they would be if the dust was not there.