Cape Rebels flag (Vryburgervlag)
The flag is similar to Vierkleur (“Four colours”), but with orange instead of red. It was used during the Second War of Liberation (1899 - 1902) by the White Afrikaans population of the Cape who fought on the side of the Boer republics. The flag can be viewed as a Boer flag since most of the Cape Rebels were Boers from the northeastern Cape frontier while a much smaller number of rebels were from the much larger Cape Dutch population of the south western Cape region.

[Article by Ron of “Republican Trekker Volk” website]

Other articles on same theme on “Volkstaat”:
The vast majority of the Cape Rebels were Boers - Ron
The Cape Rebels were not Cape Dutch