Purple CRT?

[kbmuri]

I saw this at the ETF convention over the weekend. If it had been anywhere else I'd have thought it was a practical joke. The CRT phosphors were dark purple/plum. Very strange. There were two sets like it, and a third (I believe) that was missing the tube. The commentary sheets above each claimed this type of CRT was briefly popular in Great Britain. Any AKers out there own one? Working? I'd love to see it in action.