I have the same model waiting to be built and went down this rabbit hole. Part of the problem is that the British tank museum read some descriptions of people who operated in or around the tanks and they all said something like “duck egg blue” or “sky blue”. So when it came to paint their preserved Matilda tank they painted it with a best-guess shade that people later argued wasn’t correct, but because it was in a museum it must have been right and it’s been replicated on models and depictions ever since.