Um, sort of. I think he is a grey, but also max sabino so most of his body is white hair, pink skin from birth, and the few bits of dark colouring have greyed out
Quite possibly - it depends on the colour of the skin underneath. If it is black / grey the horse is correctly described as a grey. If it is pink or unpigmented then they are correctly described as white.
There was a question about this before and I think the answer is that he is white, he is described as white on his passport details which would have been done soon after birth.
Thorougbreds are well known for having a lot of novel white (W) mutations. Wet pictures are very useful for telling, describing him as white is certainly correct
There is the odd one out there. There was a white colt by Presenting a few years ago (born white) - he did show a bit of ability but was injured. Windsor Park Stud in New Zealand have a white mare called The Opera House and she has had three white foals on the trot although she and the foals all have pink skin.