The phenomenon of scattering of light by particles in a colloid or in a very fine suspension is called tyndall effect. The individual suspension particles scatter and reflect light, making the beam visible. The amount of scattering depends on the frequency of the light and density of the particles. As with Rayleigh scattering, blue light is scattered more strongly than red light by the Tyndall effect. Another way to look at it is that longer wavelength light is transmitted, while shorter wavelength light is reflected by scattering.
Examples of tyndall effect: Shining a flashlight beam into a glass of milk, The visible beam of headlights in fog is caused by the Tyndall effect. The water droplets scatter the light, making the headlight beams visible.