The origins of the phrase come from the UK. Prince Harry of Windsor is the second son to Prince Charles, the Prince of Wales and the late Princess Diana. Prince Harry unlike his brother has Ginger Hair and has been known by the media and press as the ‘Ginger Prince’.
The common use of the phrase ‘Ginger Prince’ used to describe a friend who has Ginger Hair caught on in the UK after this use by the press of the term. The phrase is now common across the UK and is deemed more affectionate and ironic than derogatory.
Person 1: Where’s Micky T?
Person 2: Who? You mean the Ginger Prince?! He’ll be here for Lasties fella.
(Common context of the use of the phrase)