Linked from
The 9 pages that link to Color center, each with the reason it gives.
Calcium fluorideRelated: Radiation-induced defects can change the color and transmission of CaF₂.
SapphireRelated: Impurities and defects selectively absorb light, producing sapphire’s visible hues.
SodaliteRelated: Color centers contribute to the blue coloration of many sodalite specimens.
AntozoniteRelated: Radiation-induced defects contribute to the dark coloration of antozonite.