It is likely that the choice of purple as the University's colour relates to the key role played by the Bishop of Durham in the foundation of the University (purple being an episcopal colour), as well as to the unique historical status of Bishops of Durham as Palatine Earls. The following story, recounted in Whiting's history of the University of Durham, purports to explain precisely how this shade of purple came to be adopted as the University colour. (Whiting himself had heard it from a Canon Whitley, who had been Reader in Natural Philosophy during the early years of the University's existence (1833–55).)
"When the colour of the MA hood was discussed by Senate, he [Whitley] had proposed black and amber, but was outvoted on the grounds that people would call it 'Durham Mustard', a reference to the mustard factory then in existence in the city, and possibly to the popular saying that Durham was famous for 'old maids and mustard'. Mr Telfair, university tailor, afterwards produced a piece of a purple coat which had been worn by Bishop Van Mildert, and this colour was adopted for the MA hood."
The following data are somewhat open to question; in particular, the precise colour of Palatinate purple used by the University varies a good deal. Its most long-established usage is in the University's academic dress and sporting colours, both of which use a significantly paler shade than that specified below.
Palatinate purple: Pantone number is 255C, with CMYK: 51, 91, 0, 34; RGB:126, 49, 123 and Hex: 7E317B.
Palatinate blue: closest Pantone number is 634C, with CMYK: 100, 0, 8.5, 47; RGB:0, 99, 136 and Hex: 006388.