I contacted the UK division of PPG via email, giving them the 22390 code and telling them that it was for a US built tractor. They were very responsive and we swapped a few emails which unfortunately ending with them stating the obvious, which was that it was an US colour and they were unable to help.
I then contacted PPG in the US a couple of times but they have not responded. You would have thought that an exact match can be found with the code and that PPG should be able to help. The challange is getting through to the right person. Whilst typing this a thought has dropped into my head. I will contact PPG in the UK again and ask for contact information for the US office.