Ink composition

An ink composition for a marking pen consisting of a substantially odorless and nontoxic aliphatic hydrocarbon solvent having dissolved therein 5 to 35% by weight of a resinous binder in the form of a rosin derivative and 5 to 20% by weight of a modified dye, all % weights being based on the weight of the composition, said modified dye being a reaction product obtained by reacting (a) an anthraquinone dye having at least one group of --CO.sub.2 M and --SO.sub.3 M in the molecule wherein M is an alkali metal with (b) an organic ammonium compound represented by the formula ##EQU4## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are respectively a hydrocarbon radical having 1 to 40 carbon atoms, a radical of a hydrocarbon bonded to a hydrocarbon by a divalent group of --O--, --S--, --COO--, --CONH--or --NH--, the total carbon number of both hydrocarbons bonded being in range of 2 to 40, or ##EQU5## R' being an alkyl having 1 to 15 carbon atoms or an alkenyl having 1 to 20 carbon atoms, provided that the total carbon number of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is in the range of 11 to 55 and X is a halogen atom, said modified dye having a high solubility in said solvent whereby drying of the ink in the pen nib is minimized.