Black for the Hanovers
The House of Hanover and their followers traditionally wore a black cockade. A British source in 1902 tells us how it came into being.
"In the Georgian days, [that is, the time of the Hanovarian Kings George] when the troops wore the old three-cornered hats, these required, for the purpose of aiming along the musket, that the left side should be looped up, and this was done by a brooch. Anyone who has ever looked at a soldier's uniform knows how every opportunity is taken of using the Royal Crown and cypher and badges, and the brooch at the side was no exception to this rule. In fact, the whole Royal Shield, surrounded by the Garter and surmounted by the Crown, shows, if silhouetted, the basis of the fan-shaped military cockade, and it was this metal ornament at the side of the three-cornered hat that was the original of our cockade.
"The white cockade of ribbon being the badge of the Jacobites, [the Stuarts] the black metal brooch-ornament, which, as part of their uniform all the Royal troops wore, very naturally was accepted as the badge of the other side, and, without any formal intention and certainly without the slightest regulation or initiation for that object, it became 'the black cockade of Hanover.'"