I remember the panzer targets in Morsko 2006 - specifically the reducing rings. After half a dozen hits on the paddle it was grey on grey. Even hits on the faceplate were impossible to see. This, I guess, is another card up the course builders sleeve. So, blue on grey isn't that bad, after all we're not at the worlds to learn are we ? I can see your point on full kills at longer ranges. White or yellow paddles usually retain a reasonably good picture of the KZ - which is all that matters. My beef is that the colour combo should be standardised, along with 25 & 40mm KZees - but that's a springer for you and another arguement
You need two things in life - WD40 & duct tape. If it moves and it shouldn't, use the duct tape. If it should and it don't, use the WD40.