Hello Parkbremse
Such a good example of the ridiculous situations being created by the UK CAA. I think from what I understand of your situation , if the UK issued a class 1 medical before on the basis of a passed HWL then to have it revalidated it will not require you to redo any colour vision test as the HWL pass should be on record and you have no clinical indication that would require you to be retested .
I would also recommend having a look at ecdaa.com , someone with a great amount of aviation experience like yourself would be a great addition to the panel. Plus there are loads of useful blogs on colour vision testing and regualtions making it easier to intepret and understand and a dedicated forum where members can interact .
Let me know if you have any further questions I'll be more than happy to help!