expression, ichidan verb
become frantic; get excited; have one's eyes light up
Idiomatic expression describing a sudden change in demeanor due to strong emotion, such as anger, excitement, or intense interest. Often used when someone becomes visibly agitated or obsessed over something.
彼はお金の話になると目の色を変える。
He gets all worked up when it comes to money.
彼女は新しいゲームの話題で目の色を変えた。
Her eyes lit up at the mention of the new game.