AnotherEmma has summed it up well. There is a point where Lord Boreal, explicitly utilises his privilaged position in our world (not Lyra's), which when talking about old monied, aristocratic influence does tend to infer being white. I imagined him older (middle aged, well established with self confidence broaching into arrogence) too for reasons of interactions between characters.
The actor is doing a good job of playing him now I've had a couple of episodes to settle in, but I found it was surprising casting on my first impression based on my understanding of the trilogy (I was surprised to see him introduced in ep1 anyway).
There is a lot more space for artistic license with the gyptians who have their own distinct culture (and the introduction of the dæmon settling/ ring ceremony set a tone on that). Farder Coram is presented as being infirm due to old age, but the descriptions of his dæmon allude to the type of character he was in his youth.
I think the magisterum has to be very heavily masculine. It has an affect on the existence of organisations like the General Oblation Board.
There was a reason why the Catholic Church was less than enthused about these books... for some reason it was taken a little personally 
I suspect Ma Costa will have a more prominant role through the series than in the books where she was vetoed, which is probably one reason for a younger, edgier casting choice than the older, more buxom type of character that a few of us visualised.
It is so tough creating a TV/ film version of a well-loved book when the book has been visualised in so many parallel universes of the readers' minds.
Casting Harry Potter films had the benefit of the books being less established by the casting of the first film and many people being introduced to the films then the books. Viewers were a lot less entrenched in the vision that they had held from childhood into adulthood... that would be different if they were remade now.