ORANGE
After the Union of the Crowns in 1603, the House of Stuart ruled all of England and Wales, Scotland and Ireland. The Stuarts married into other European dynasties, including the House of Orange-Nassau, which was founded in 1544 and survives today as the Royal House of the Netherlands.
These two royal houses maintained close links throughout the seventeenth century, culminating in 1688 – 9 when the ‘Glorious Revolution’ brought William of Orange and his wife Mary Stuart jointly to the throne of Britain as William III and Mary II.
Orangemen (n.)
https://www.etymonline.com/word/Orangemen
1796 in reference to members of a secret politico-religious society founded 1795 in Belfast to promote Protestant power in Northern Ireland, named for William of Orange (who became King William III of England and triumphed in Ireland at the head of a Protestant army at the Battle of the Boyne), of the German House of Nassau. His cousins and their descendants constitute the royal line of Holland.
The name is from the town of Orange on the Rhone in France, which became part of the Nassau principality in 1530. Its Roman name was Arausio, which is said in 19c. sources to be from aura “a breeze” and a reference to the north winds which rush down the valley, but perhaps this is folk etymology of a Celtic word. The name subsequently was corrupted to Auranche, then Orange.
The town has no obvious association with the fruit other than being on the road from Marseilles to Paris, along which masses of oranges were transported to northern France and beyond. In this roundabout way the political/religious movement of Northern Irish Protestantism acquired an association with the color orange, the Irish national flag acquired its orange band, and Syracuse University in New York state acquired its “Otto the Orange” mascot.
Wasn't that when Parliament (the legislative branch) assumed the power to determine who was the rightful king?
I think you just uncovered the meaning of orange to these people.