Let’s get through this with as little intense fictional verbosity as possible, because as we all know, high concept fantasy stories can be a little heavy due to exposure. It’s fun, but not for everyone.
As mentioned earlier and as shown in the second season of the Netflix series, Geralt’s aesthetic is unique among witchers. No one else, thanks to their status as a witcher, is rocking gray hair and golden eyes, and that’s because no one has had to go through the same process as Geralt. At least not completely.
To become a Witcher, prospective candidates (read: children, this is done with literal children) must pass the Trial of Herbs. As detailed Sideshow, this test, which is actually a series of experiments, is incredibly painful and comes with a high death rate. Indeed, a very high mortality rate. However, those who survive come out the other end with superpowers. Geralt not only survived the process, he somehow succeeded. He was so unfazed by the Trial of Herbs that he underwent further experiments to test his abilities. These further experiments resulted in his unnaturally white hair and golden eyes, which in the Netflix series are achieved with practical makeup.
Considering the whole ordeal was almost certainly excruciatingly painful, it’s unlikely that others would be interested in following suit, but let’s be honest – naturally white hair and golden eyes are an aesthetic that cosplayers spend serious money on. If such tests were available in our world, there would certainly be volunteers.