Abstract: A method for dyeing a textile substrate, in particular for dyeing a textile substrate with reactive dyes, is described in which the textile substrate is brought in contact with a dyeing liquor containing at least one dye and after a predetermined dyeing time has elapsed, the dyed textile substrate is rinsed. The at least one dye which has not been fixed by the textile substrate and is present in the dyeing liquor is destroyed by a chemical and/or physical treatment to such an extent that the dyeing liquor is largely colourless hereafter, whereby the textile substrate being rinsed with the largely decolourised liquor. A device for carrying out the method comprises a vessel for receiving the textile substrate to be dyed and a circulation system for the dyeing liquor, where a reactor through which the dyeing liquor flows is assigned to the vessel and/or the circulation system and where inside the reactor the chemical and/or the physical treatment of the liquor to be decolourised is carried out.