Andy, I’ve put a note about this on Dockside before, but I think it’s worth repeating.
I’ve been very lucky to have had two good sailing friends who were Cunard Masters. One of them was “Staff Captain” on Caronia and Carmania at times, and the continual repainting was one of his bugbears.
Aquiring the paint in Cunard colours was very much left up to the local agents around the world, and he then had the responsibility to approve the mixes of the three greens and organize keeping a smart ship. He said with a twinkle in his eye that it was part of his job to ensure nobody could see both sides of the ship at the same time!
I took his advice on the funnel red as well - although it always started off as a bright Post Office / Ferrari Red he reckoned it only took a couple of weeks for the sun and salt to turn them matt orange. So your sun blanching is prototypical…..