Imagine there was a society in which blue eyed people are referred to with blee/bler pronouns, and green eyed people are referred to with glee/gler pronouns, and one day someone from that society saw a brown eyed person and had no idea whether to categorise them as blee/bler or glee/gler
I got confused at first because I didn’t know about that Sanderson book series and thought you were talking about The Lightbringer Series by Brent Weeks. They develop colored rings (in their eyes) based upon the light spectrums they use, each with their own properties. Their nobility or such being those who use multiple colors and usually their is one Prism, who can use the full spectrum of light. (It touches on a couple outside out view like sub red and ultraviolet as well). Had been awhile since I’d see mention of those books