Why the names - Blue Steel, Blue Streak, Black Prince, Black Knight, Black Arrow and so on?
For security reasons, all the British defence projects of the 50s and 60s were given "colour" code names - i.e., a colour followed by some meaningless word. Thus, running through the spectrum, we have Red Snow, Orange Herald, Yellow Sun, Green Granite, Blue Water, Indigo Hammer, Violet Club, and so on. There were only two official "Blacks" - Black Knight and Black Arrow. Black Knight was not a weapons system but a test vehicle. Black Arrow was entirely civilian. There was never a "White", to my knowledge.