The ink of the invention comprises (a) a vehicle comprising (1) about 1 to 50 wt % of at least one organic solvent as humectants, and (2) about 0.01 to 20 wt % of at least one water-soluble surfactant or amphiphilic polymer (cationic, anionic, or non-ionic); (b) about 1 to 20 wt % of at least one partial chemically-modified, water-soluble colorant, the colorant having sufficient functional groups associated therewith to be substantially waterfast in deionized water while being sufficiently stable in the ink to avoid flocculation; and (c) the balance water. The use of a partial chemically-modified, water-soluble colorant (macromolecular chromophore) results in an ink that is both waterfast and non-flocculating.