@madra_b hi, I don't know if u still don't know but yes, you're right. In the novel, the Crown Prince, it's said to have silver hair, so he's the last guy (he's supposed to be the most handsome one and I think it matches here as well); the Duke is supposed to be blonde but here (the 1st guy who appears after the girl) he looks more like brown-haired.
Also in the novel, there's that phrase of a sincere friendship, a sincere relationship, and a sincere love, which matches quite well with the characters' characteristics.
@AiriAi Oh yes I did finally figure it out. I had to read pretty significantly far in the novel to finally get the hair description between the two characters. Or I just didn't read well enough before and missed it . Thank you!