Like Cithrel has harsh, light, uncommon eyes to enhance their weirdness and link with Hatred, and the fact they're scary, and the specs of blue are due to Hatred but they're just specs because Hatred isn't fully there
And Kyeran's eyes are a play on "Windows to the soul" thing, because yk dark eyes but actually he's nice but he thinks they show that he's not actually so it's another thing he shames himself for despite not being able to do anything about it
And Nurath has warm brown eyes because she herself is a warm person but also because, being castless, she's supposed to be the "no one girl", except her warmness and openness are part of what makes her special and her eyes actually denote from others around her
And Alanis has green eyes because his a dreamer and an elf, so it's a way to show his connection to magic and potentially ancient one as well, but it's a warm and very earthy green because it's important, essential even, that he's also from this world...