sentences:  Even fractions of parhelic circles are less common than sun dogs and 22° halos.While parhelic circles are generally white in colour because they are produced by reflection, they can however show a bluish or greenish tone near the 120° parhelia and be reddish or deep violet along the fringes.Parhelic circles form as beams of sunlight are reflected by vertical or almost vertical hexagonal ice crystals.