More specifically, the basic heterocyclic diazo dyes of this invention, including Basic Blue 93, are characterized by formula I or II: ##STR1## wherein R is a lower alkyl or benzyl radical, Z?? is an anion such as chlorine, and B is a radical having the formula: ##STR2## wherein A is a phenylene or naphthylene radical and R1 and R2 are the same or different, and are selected from the group consist