Free amine-containing polymeric dyes

The process for water fast coloring a proteinaceous fiber substrate which comprises applying to said substrate a solution comprising a solvent selected from the group consisting of water of pH 2.0 to 4 inclusive and a water-organic solvent containing up to 80% by weight of a member of the class of 1 to 4 carbon alkanols, ethylene glycol, propylene glycol and 3 to 5 carbon alkanones, and dissolved therein from 100 ppm to 0.5% by weight of a polymeric colorant comprising a hydrocarbon polymer backbone to which is covalently bonded through amine linkages a plurality (m) of essentially anionic group-free optically chromophoric groups and to which is also covalently bonded a plurality (n) of free primary or lower alkyl secondary amine groups, wherein n is not less than 1/2 m, and n and m are such that their sum is from 20 to 3000 and the polymeric colorant has a molecular weight of not less than 2000 daltons and thereafter rinsing the substrate with water and drying the substrate.