A process for preparing a colorant of the formula ##STR00001## which comprises preparing a first reaction mixture by admixing leucoquinizarin and, optionally, quinizarin, an aminobenzene substituted with an alcohol group of the formula --R.sub.1--OH, boric acid, and an optional solvent, and heating the first reaction mixture to prepare an alcohol-substituted colorant of the formula ##STR00002## followed by converting the colorant thus prepared to either an ester-substituted colorant by reaction with an esterification compound which is either an anhydride of the formula ##STR00003## or an acid of the formula R.sub.2COOH in the presence of an optional esterification catalyst or a urethane-substituted colorant by reaction with an isocyanate compound of the formula R.sub.4--N.dbd.C.dbd.O and brominating the colorant thus prepared, wherein either conversion to ester or urethane can be performed before bromination or bromination can be performed before conversion to ester or urethane.