I have this head cannon about Romano's eyes, you might have heard it before, I don't know if it was already a thing, but this is what I believe.

There is a lot of contradictory about Romano's eyes, and when I say that, I mean their color.

Emerald green, like Spain, the man who raised him.
Hazel/medium brown, like Veneziano, his fratello and his 'other half'.

Think which ever one you like, but I really couldn't decide which I liked better, because both eye colors suit his personality. So, that's where this came from.

I think Romano has both eye colors. As in, they change colors. And not just at random times, but according to his emotions.

When they are emerald green, he has a lot of passion within him, whether it be anger, hatred, frustration, agony, dedication, joy, excitement, etc. Anything that involves a lot of emotion in it.

When they are hazel/medium brown, he is in a more calm or relaxed kind of mood, like when he is thinking, sad, happy, kind, doing his work, or even simply being alone.

Then there are moments when he will have a mixture of those colors, and depending on what he is feeling, it will lean slightly towards either color. Like if he is confused, it will be hazel with hints of light green, or if he is conflicted, they will be green with specks of gold in them.

This might have been a little confusing or boring, but I always found it interesting. Let me know what you think, and the next chapter is going to be a 2p character, just a heads up ;)