There was no dominant colour scheme pre-2000, from what I've heard.
Well, across the world, red is used for left wing parties historically, especially those calling themselves socialist.
I know that in Canada,
les rouges et les bleus dates back a LONG time (red for the Liberals/Grits, blue for the Conservatives/Tories). It was well enough established that when an avowedly Socialist party came along (the CCF, now NDP) came along they had to use other colours. A quick Google shows the "parti rouge" was established in 1847, as a successor to the "parti patriote" in Québec.