The high quality of the annatto dye (Bixa orellana L.) and the plethora of products derived and used from this plant in Pre-Columbian and Colonial times are reflected in numerous ethnohistorical writings that were redacted in the New World throughout the sixteenth, seventeenth and eighteenth centuries. Those manuscripts reveal abundant information about the methods employed with annatto to obtain the dying substances: orelline and bixin, which was classified as a lesser or false dye in the techical manuals published in eighteenth-century in Europe, it is mean, as one of the many dyes of unstable nature that were so widely employed to obtain different hues from the same colour and reduce costs. On the other hand, the particularly warm and bright colours produced by annatto on mixing with different concentrations of other colourants goes to explain why it was one of the most appreciated and used dyes in Pre-Columbian and Colonial textile and painting art. The study of the annatto considering the dye tradition in ancient America and Europel, the close lecture on those ethnohistorical writings, and the chemical-analytical knowledge recently, has made it possible to present this paper, which provides to the specialists in conservation-restoration and history of art an important information and a detailed study about the origin, properties and uses of one of the oldest and most highly valued colourants in America and Europe.