I have noticed that a lot of CRTs have a coloured coating inside of them that would appear to have practical purpose other than maybe protecting the aquadag. Paints and plastics tend to be avoided in vacuum scenarios, so I can't imagine that the green coating is paint. Would anyone happen to know what the green layer is and why it's there?
To be clear, I know from breaking one of these open that it's a flat layer of green. In this image, the CRT PDA (The black lines) is helical, but I've also seen this green in banded PDAs.