ond reaction mixture to form an ester-substituted colorant of the formula [0071] and (c) forming a third reaction mixture by admixing (1) the ester-substituted colorant, (2) bromine, and (3) a solvent followed by quenching the third reaction mixture with water to form a brominated ester-substituted colorant and a salt thereof, of the formulae [0072] and [0073] wherein Y is a hydrogen atom or a bro