Pilot bottled ink iroshizuku
tsuki-yo (Moonlight)

"tsuki" is a moon and "yo" is a night.
I think there are various perception of color of moonlight.  "tsuki-yo" is a very slightly greenish blue-black.
Japanese often say "greenish black hair", to express a beauty of purely black hair of women.  From things like this, I feel Japanese heart in hidden green of this blue-black.