Oh, fascinating! I hadn't thought of that. The current worldbuilding in the book is such that only super-powerful Cardinal Psy get those eyes (which also go pure black with rage or sadness I think), and since the Psy don't do emotion, they also usually don't do sex. And, of course, it's a romance novel, so you know, women ALWAYS orgasm when they have sex with their True Love! It's a Sign!

But that would be really really interesting, and I'm especially curious if the rainbow eyes come out if you're having sex and orgasm period, or if it's only if you orgasm with your True Love, etc. etc.