I’m not sure why cannons welcome you to the zoo, but that’s the way it is down here. I guess the cannons relate to the cyclorama, as they share an entrance, but most people go to the zoo. Especially since the cyclorama is closed on Sundays (of all things given the zoo crowds; probably with budget shortfalls, too).
Anyway, this is a view up from below the cannon barrel. Rainfall tracks. Patterns distorted by the slight upward angle of the barrel.
I would have said this meant green-grey, but no, my sources say it’s a corruption via Middle English of the Old French vert de Grece, or green of Greece.