I feel like I end up repeating myself, but once again: there cannot be a 1:1 transformation from one medium to another. The games - they are not canon. They are what CDPR made of the characters. Even if the books described $PERSON as looking like something, the image you have of him/her is just what is your interpretation of him/her is. "Sin City" is the only example I can think of where there has been a successful transformation from one media to another; and yet, there are differences (and the source material was a visual novel).
So, let's wait for the end result, before we get too worked up. Who knows, the character who plays Fringilla may end up being terrible, in which case I'll rightfully deride her. Or, she may up being a great actor and have some awesome scenes I'll remember years on. As said, who knows. But if you want to experience everything like you did when reading the books... I dunno, read the book? There will be deviations from what you expect, and I doubt skin colour will be the largest among them.