Colorants, in paricular, carminic acid and indigotine are widely used in pharmaceutical industry. High concentration of these colorants affect human health that require a control of their content in pharmaceutical dosage forms. In current work, novel voltametric sensors based on glassy carbon electrodes modified with selenium dioxide nanoparticles dispersed in surfactant media have been developed for the determination of carminic acid and indigotine. Combination of selenium dioxide nanoparticles with surfactant media provides stabilization of nanoparticles dispersion by suppression of their aggregation as well as action of the surfactant as a co-modifier of the electrode surface, i.e. as a part of sensing layer of the electrode. The effect of surfactant nature (cationic, nonionic, and anionic) and concentration on the colorants' voltammetric characteristics has been investigated. The best response of colorants has been obtained in the case of selenium dioxide nanoparticles dispersed in cationic surfactants (0.10 mM cetyltriphenylphosphonium bromide for carminic acid and 1.0 mM cetylpyridinium bromide for indigotine). The sensors developed have been used under conditions of differential pulse voltammetry in acidic medium. A linear dynamic ranges of 0.010‒2.5 and 2.5‒10 μM of carminic acid and 0.025–1.0 and 1.0–10 µM of indigotine with the detection limits of 3.4 and 4.3 nM, respectively, have been achieved that are the best ones among the methods reported to date. Another advantage of the sensors developed is a simple one-step fabrication as well as easy and fast preparation of the modifier. Sensors have been successfully applied in the analysis of pharmaceutical dosage forms (vitamin tablets, capsules, and lozenges for sore throat treatment) and validated with spectrophotometry. The direct analysis of colorants in various pharmaceutical dosage forms confirms versatility of the sensors developed that can be used as an alternative method for the quality control of the pharmaceutical products.