Colorant-containing aqueous polymer dispersions comprise (all amounts by wt. of polymer matrix): (A) (i) a polymer matrix based on an ethylenically-unsaturated monomer (M); and (ii) an organic colorant comprising a dye or pigment, UV-absorber or optical brightener uniformly dispersed in the polymer matrix (0.5-50%); (B) a nonionic surfactant (0.1-20%); and (C) an amphiphilic polymer with 0.5-10 mol./kg anionic-functional groups (1-50%). An Independent claim is also included for preparation of the dispersions by: (i) dissolving the colorant in monomer M, (ii) emulsifying the mixture to give a conventional oil-in-water emulsion, (iii) homogenizing to give a mini-emulsion with monomer droplets of average diameter below 1,000 nm and then (iv) polymerizing the mini-emulsion in presence of a soluble free-radical initiator together with (B) (0.1-20 wt.%) and (C) (1-50 wt.%), each wt. being based on the wt. of M.