The lime stick figure was building a random structure with the creative mode menu from the Minecraft block he was using. He slightly turned his head towards you, giving you a small wave, and continuing to build.

His building speed quickly slowed down as he realized you weren't Orange (The Second Coming), Red, Blue, or Yellow, and instead someone else he hadn't seen before...

Green turned back around to face you, looking at you in silence for a second, before...a text box suddenly appeared above him, with the words in the text box saying: "Uhm...hello?", probably as a way to compensate for his lack of ability to talk.