Green
He resents that term - what he really is - what he denies being - green-eyed monster. Yes, yes, his irises are green - so are the Princess's (she is a beauty, not a monster).
He pretends to be mildly interested when she brings up all the friends she makes on Earth. He blinks when she mentions Kaizuka Inaho with reverence and how a filthy terran (like him) saved her life.
His eyes give him away.
Worse still was knowing that she spent her virgin trip to Earth mostly in the company of that rotten Orange. And enjoying it, for the most part.