After him saying it was his natural colour, it is thus the only correct option. I did have spotted for a little while cause I absolutely love spotted cows cause they're what I grew up with.
Also I like Greek myths. What's so funny is like 95% of minotaur depictions, even the ones based solely off the myth, always have brown or black fur despite the fact that the myth specifically says that the father bull was indeed white.
It's like the opposite of the biblically accurate angel meme. Yes some angels looks like that, but not all. Asterion having white fur is myth accurate and I will never not be a tiny bit amused by that.