A plethora of multicolored dots.

I would say that it was a painting made by Gamzee with the blood of his fallen trolls, but some of these aren't official blood colors.

Gamzeee not only uses blood to draw on walls.

Blood isn't the only thing Gamzee uses to paint his walls with

Gamzee about to poke some Apple Juice that has some holy lights around it

gamzee pokes a jar of dave's "applejuice"

Gamzee suspiciously staring at apple juice: "This dun look like no faygo..."

Gamzee realizes apple juice is in fact, not his faygo.

gamzee does not like apple juice, it was piss