Let's get through this with as little intense fictional verbiage as possible because — as we all know — high concept fantasy stories can get a little heavy with the exposition. It's fun, but it's not for everyone.
As previously mentioned, and as displayed in Season 2 of the Netflix series, Geralt's aesthetic is unique among Witchers. No one else is, by merit of their status as a Witcher, rocking the white hair and golden eyes, and that's because no one else had to undergo the same process as Geralt. Not completely, at least.
To become a Witcher, potential candidates (read: children, this is done to literal children) must survive the Trial of the Grasses. As covered in-depth by Sideshow, this trial — which is really just a series of experiments — is incredibly painful and comes with a high mortality rate. A really, really high mortality rate. However, those who survive come out the other end with superpowers. Geralt not only survived this process, he somehow thrived. He was so unperturbed by the Trial of the Grasses that he was put through further experiments to test his abilities. These further experiments lead to his unnaturally white hair and golden eyes, both of which are achieved in the Netflix series via practical makeup.
Given that the whole ordeal was almost certainly excruciatingly painful, it's unlikely that others would be interesting in following suit, but let's be real here — naturally white hair and golden eyes are the kind of aesthetic that cosplayers spend serious coinage on. If similar trials were available in our world, there would absolutely be volunteers.
