sentences:  Therefore, a black (fully oxidized) tea often appears red while a green or white tea has a much clearer appearance.The colour of a black tea, however, is affected by many other factors as well, such as the amount of theaflavins, another oxidized form of polyphenols.Thearubigins were first studied by Roberts, E. A. H. in the 1960s by the means of spectroscopy or by fractionation or paper chromatography.