Synthesis of some new hetarylazoindole dyes have been carried out by diazotization. of 5-substituted 2-aminothiazoles in nitrosylsulphuric acid and coupling with various 2- and 1,2-disubstituted indole derivatives. The structures of the dyes were confirmed by UV-VIS, FT-IR, and H-1 NMR spectroscopy as well as by LC-MS or MS spectrometry and elemental analyses. The solvatochromism of the dyes was evaluated with respect to the absorption properties in various solvents. Absorption maxima of the dyes generally did not changed with the polarity of the solvent. The color of the dyes is discussed in relation to the substituents in the thiazole ring. The effects of an acid or a base on the visible absorption maxima of the dyes are also reported. In addition, the absorption spectra of the dyes were compared with those of corresponding model compounds, which do not exhibit azo-hydrazone tautomerism.