I had a CRT portable as main telly for years as it didn't get much use. After a decade, something was starting to give and a purple splodge developed in the top left hand corner and grew over the years. I was fine with it but partner, visiting parents etc were becoming increasingly frustrated. Anyway, snooker-wise, the white would start off white and gradually turn pink then purple the closer it got to top left of screen then white again as it moved toward the blue. The yellow, on its spot, was a sort of washed out pinkiness. I like to watch a frame or two but then start to realise again that once you've seen one you have, pretty much, seen them all.