A process for the coloration of a hydroxy substituted organic polymeric substrate by heating it to at least 93.degree. C. with a water-soluble dyestuff containing one or more groups of the formula: ##STR1## WHERE M is a metal N IS 0 OR 1Q is 0 or 1M is 0, 1 or 2R = 1 or 2T = 0 or 1And r+t is not greater than 2 and when n = 1, m+t+r+q is not greater than 3, in the presence of a carbodiimide and a salt or a volatile amine.This process is valuable for coloring, in particular, cellulose textiles. It permits the use of dyestuffs in the form of metal, especially sodium salts, thereby avoiding the necessity of having dyes as free acid or ammonium salts which related known processes require.