Abstract: A printer ink composition containing a triphenylmethane dye or a lake pigment derived therefrom as a coloring agent, including as the coloring agent a triphenylmethane dye having general formula (I): ##STR1## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen atom, an alkyl group, an aralkyl group or an aryl group, R.sup.5 is an aryl group, X.sup.- is a counter ion, and ring A or ring B may be substituted by one or more substituents, provided that at least one group among R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is not methyl and in the case that R.sup.5 is p-dimethylaminophenyl, at least one of R.sup.1 and R.sup.2 and at least one of R.sup.3 and R.sup.4 are not methyl; or a lake pigment derived therefrom, in order to prevent the formation of Michler's ketone. The ink composition is used for printing media for printer such as fabric ink ribbon, ink roll, ink-retaining element, thermal transfer ink ribbon, and pressure-sensitive transfer ink ribbon.