Robert Geißler was the first person to produce a colour reproduction(1) of the painting. In 1868 he published a 5-colour lithography: crimson, blue, yellow, dark brown and white. Nobody would accuse these little pictures (about 12 * 5,5 cm) of being great art — but they may be our best witnesses to the original colours.
The Duke and "his" Death are white since they had been removed from the painting in 1799. This might indicate that Geißler has been careful about rendering the colours authentically.
On the back of the folder one finds the "new" text from 1701 and as much of the medieval text from 1463 as remains.