For the efficient preconcentration of azo compounds – products of the interaction of 4-nitrophenyldiazonium with thymol, a system 4-nitroaniline (4-NA) – NO2- – Triton X-100 – NaOH – ethanol has been proposed. The optimal conditions for the formation of micellarsaturated phases of the system under study have been established: 3.10-4 M 4-NA – 3.10-4 M NO2- – 5% Triton X-100 – 2.8 M NaOH – 10 vol. % С 2Н5ОН. A spectrophotometric study of the above system has been carried out. A linear dependence was built in the coordinates A (at λ max = 552 nm) vs с(thymol), which is described by an equation of the form A = f(c), A = 26291c + 0.02; R2 = 0.997. The range of the determined contents of thymol is (2·10-6 – 4·10-5) mol/l. A technique for the colorimetric determination of thymol in aqueous media (color channel G) has been developed. The intensity of the channel G chromaticity (IG) is linearly dependent on pc(thymol) in accordance with the equation IG = 54.2pc – 267, R 2 = 0; the lower limit of the determined contents of thymol is 1.10-6 mol/l, which is two times less than in the variant of its spectrophotometric determination. The profiles of petal diagrams in the color coordinates of the RGB CMYK model have been constructed; the dependences of their area (S) and perimeter (P) on the thymol concentration have been obtained (P: y = 278x – 10.13; R 2 = 0.97; S: y = 20182x – 87649, R 2 = 0.99).