It was on this day that the aforementioned Duncan was slain in battle by Macbeth's forces at Bothnagowan or Pitgaveny near Elgin in Moray.
If you think of Macbeth then your mind automatically thinks of William Shakespeare who used Raphael Holinshed's Chronicle of Scottish History as a basis of his famous play and it is from his work that we, on the whole, view Duncan and Macbeth. Holinshed's work and Shakespeare play should be taken with a pinch of salt, they were written over five hundred years after the event. Shakespeare wrote Macbeth when James I of Scotland was on sitting on the English throne.
There is a painting of a dark-haired bearded Duncan depicted as one, among ninety-three other paintings, of Scotland's heroic kings, it has him wearing a red cloak over his armoured shoulders (the image below is probably based on this work)
Duncan's portrait has the following inscription -
'Son of Beatrix, daughter of Malcolm II a good and modest Prince. He was slain by Macbeth, traitorously, in the 6th Year of his Reign’ Duncan I is number eighty-four in the series.