Red natural anthraquinone dyes on ancient textile materials can be readily identified by thin-layer chromatography (TLC) if they belong to the class of madder dyes. The method also shows which type of dye plant from the family Rubiaceae has been used for dyeing (<i>Rubia tinctorum</i> L., R. <i>peregrina</i> L., R. <i>cordifolia</i> L., R. <i>akane</i>, various <i>Galium</i> spp., <i>Relbunium</i> spp., <i>Morinda</i> spp., <i>Olendlandia</i> spp., <i>Coprosma</i> spp., or <i>Ventilago</i> spp. (Rhamnaceae)). Any changes in the composition of the dye during its extraction from the dyed material, e.g., the transition from pseudopurpurin to purpurin, can be prevented by suitable preparation of the sample before TLC. The red insect dyes from <i>Dactylopius coccus</i> Costa (American cochineal), <i>Kermococcus vermilio</i> Planchon (kermes), and <i>Kerria lacca</i> Kerr (lac dye) can also be readily distinguished by TLC comparison. <i>Porphyrophora polonica</i> L. (Polish cochineal) contains small amounts of the kermes dyes kermesic acid and flavokermesic acid besides the cochineal dye carminic acid. These secondary components cannot be identified unless they have previously been concentrated. <i>Porphyrophora hameli</i> Brandt (Armenian cochineal) contains nearly exclusively carminic acid. It has been reported that high performance liquid chromatography has also identified a trace of kermesic acid, but TLC has not provided any clear proof of the presence of this secondary component in Armenian cochineal, even after previous concentration.