The amount of paper dyed is increasing each of the last few years, mainly because the increasing consumption of corrugated board papers. Paper is colored by dyes of different chemical nature – inorganic pigments; synthetic organic pigments; basic, acid, direct dyes and others. The reactive dyes are capable of forming covalent dye-polymers bonds, for instance, with the hydroxyl groups of cellulose. In this experiment are being used two laboratory synthesized reactive dyes, derivatives of chlorotriazine and one of them contains a stabilizer fragment. Dyes are used in the composition of offset printing paper with a fiber content of bleached softwood and hardwood pulp in a ratio of 1:1. The paper is sized with alkyl ketene dimer and as filler is used natural calcium carbonate. The strength and hydrophobic properties are being examined. The optical properties are also been examined before and after accelerated thermal ageing of the resulting paper samples and it is being found out that the examined dyes can be of an interest for an industrial production.