@terrywynne
Out of curiosity, is there a theory about why colour blind casting has been more acceptable on stage? Six and Hamilton but being prominent examples but also loads of examples in regional theatres etc.
Is it because film is designed to feel more 'real where stages make you feel you are watching theatre so you suspend disbelief?
I mean, in the examples you've given, the minute people start singing

I remove all expectations of authenticity and then just enjoy the 'spirit' of the performance so the race of the actors becomes almost immaterial. Because one thing I'm pretty sure of was that Henry VIII didn't rap his way through his marriage troubles.
Same with something like Sofia Coppola's Marie Antoinette where the deliberately anachronistic music/costume etc showed that she was aiming to represent the feeling of the period rather than true historic verismilitude, and as I said above, Merlin with a talking dragon rendered a black Guinevere unremarkable.
Even with 'normal' plays you are already employing a level of fantasy when you "accept" that that painted cardboard wall is actually a house, or those men carrying sticks are really a forest, etc., so you are already accepting a certain level of variance from strict realism, so you can accept that x actor is just 'representing' this character, just like the wall 'represents' a house, etc.
Whereas if it's a 'serious' BBC (or whatever) historical drama that otherwise does appear to aim for realism and the idea is that you are supposed to be completely sucked in to the drama, I suppose you do sort of expect that to extend to everything...which is why people get so excited about pointing out historical anachronisms and missed water bottles etc 