The tune is the Black Joke or Joak which derives from a bawdy 18C song which is in the DT - Black Joke and The Coal Black Joak. It seems to have resulted in lots of imitations at the time including Red, White, Yellow and Brown Joaks (but not Green so far) which I've found the dots to. They all seem to have the characteristic of having peculiar numbers of bars in one or more of the parts but are in various time signatures.

There is also a True Joak recorded by John Kirkpatrick which has the same characteristic. I've also come across references to Blue and Grey Joaks and a few uncoloured ones.

Not sure if any of this is remotely relevant but there you go.