Very recently a work by Zhu and co-workers has been published, aiming to develop a theoretical protocol for color prediction of sulphonated azo dyes, based on 3, in water. In this work a very detailed theoretical consideration was made, but only on the azo tautomers of the studied dyes. The hydrazo forms, in which they really exist and which is mainly responsible for the color and practical use of this class of compounds, are totally neglected. The overall hypothesis, based on neglecting the physical and chemical background of the properties of azo dyes, is, if not useless, at least doubtful. Therefore in the current critical note the tautomerism of the dyes, described in , will be considered along with how it affects the color and the spectral properties. For this purpose, the existing, in the literature, experimental data will be used and interpreted with the help of theoretical calculations.