I don't get it either but I'm too curious not to approve it.
Go-hako desuyo!
Ketsui's score chips are often called "Hako". (lit. "box")
For example, 5-chips are called "Go-hako". ("Go" means "five" in Japanese)Armored Green
Ketsui Stage two title.
It's also a parody of Edo-murasaki (lit. Edo purple), Momoya's brand name of laver boiled down in soy.