Paper coating colours exhibit complex interfacial and rheological properties resulting from the interaction between paper coating colors and yellowing inhibitors, which are added to coating colors to increase the stability of paper brightness. The zeta potential of ground calcium carbonate and kaolinite particles was measured. It was found that the zeta potential increased with the percentage of added inhibitor. Moreover, the measurements revealed the influence of adsorption of inhibitors on ground calcium carbonate and kaolinite. Rheological properties of inhibitors were measured and their effect on the rheological properties of coating formulations was investigated. The elastic character of the colour containing inhibitors was more pronounced than the viscous character. The elastic modulus and viscosity were strongly influenced by the inhibitor used. Measurements of water retention of coating suspensions showed that the inhibitor (radical scavenger) reduced the water retention of coating colors.