Why is Adeno B12 pink in color?

The Vitamin B12 (hydroxocobalamin, adenosylcobalamin, methylcobalamin, or cyanocobalamin) molecule contains cobalt (so called “cobalamins”). Cobalt can form many compounds that portray a variety of colors. When the element is combined with water, its salts form a pink color, known as a metal aquo complex. The cobalt gives the water-soluble molecule B12 its distinctive “reddish-pink” color.