I think you have a very weird way of thinking about colour. Saying the sky is blue is no different than saying the ocean is blue. Water doesn't look blue when you get something wet either, and yet the ocean is blue.
A "weird radiation thing" is exactly how colour works.
I have a blue blanket that doesn’t leave blue stains on anything either. That’s not a robust definition of what it means for something to be a certain color.
It’s because of weird radiation thing that happens in many contexts. Including the irises of people with “blue” (transparent) eyes.