The present invention relates to a water-absorbing polymer and to a process for preparation, comprising the process steps of (i) mixing (α1) 0.1 to 99.999% by weight, preferably 20 to 98.99% by weight and more preferably 30 to 98.95% by weight of polymerizable, ethylenically unsaturated monomers containing acid groups, or salts thereof, or polymerizable, ethylenically unsaturated monomers including a protonated or quaternized nitrogen, or mixtures thereof, particular preference being given to mixtures including at least one ethylenically unsaturated monomers containing acid groups, preferably acrylic acid, (α2) 0 to 70% by weight, preferably 1 to 60% by weight and more preferably 1 to 40% by weight of polymerized, ethylenically unsaturated monomers copolymerizable with (α1), (α3) 0.001 to 10% by weight, preferably 0.01 to 7% by weight and more preferably 0.05 to 5% by weight of one or more crosslinkers, (α4) 0 to 30% by weight, preferably 1 to 20% by weight and more preferably 5 to 10% by weight of water-soluble polymers, (α5) 0-20% by weight, preferably 2.5-15% by weight and more preferably 5-10% by weight of water, and (α6) 0-20% by weight, preferably 0-10% by weight and more preferably 0.1-8% by weight of one or more assistants, where the sum of the weights of (α1) to (α6) is 100% by weight, (ii) free-radical polymerization with crosslinking to form a water-insoluble, aqueous untreated hydrogel polymer, (iii) drying the hydrogel polymer, (iv) grinding and sieving the water-absorbing polymer to size, (v) surface postcrosslinking the ground and sieved hydrogel polymer and (vi) drying and finishing the water-absorbing polymer, wherein preferably 0.07 to 7% by weight of a salt of an α,β-diunsaturated carboxylic acid, based on the weight of (α1), from the group of α,β-diunsaturated carboxylic acids has been treated with the water-absorbing polymer and 0.00001 to 5% by weight, preferably 0.002 to 4% by weight and more preferably 0.007 to 3.5% by weight of a colour stab
