I always sort of figured Dracula's hair was white/gray when he was weaker. or when he doesnt keep his youth up by drinking blood.
figure, in both CoD, and Symphony, he has been prematurely resurrected. And the little Symphony manga thing shows Pre-Catslevania Dracula with his symphony design, which could simply be overlooked, but would make sense, he probably didnt actually drink much blood when he was married to a HUMAN woman who might not feel too comfortable about him feeding off of her kind like slurpees.