I was able to obtain the golden dream of HUD recoloring:
Changing the main HUD color, while also keeping RED, GREEN, CYAN, WHITE separate, often unchanged, as in RED stays RED, GREEN stays GREEN, so on and so forth.
The problem though, is these color transformations were obtained inside a graphics editing software, by applying a channel mixer, with values going between -200% and +200%. They don’t seem to work properly in-game.
My in-game testing looks different: The colors are displayed as intended on Station HUD displays, but different on Cockpit HUD displays: more red on the red channel; or it simply doesn’t apply the whole transformation range (-200% to +200 percent).