Examples of such amorphous polyesters include those obtained by the polymerization of a monomeric colorant compound, terephthalic and/or 2,6-naphthalenedicarboxylic acid and a branched-chain diol having the formula ##STR1## wherein R1 is hydrogen or an unsubstituted or substituted alkyl, cycloalkyl or aryl radical and R2 is an unsubstituted or substituted alkyl, cycloalkyl or aryl radical.