Green paint on sidewalk

The sidewalk outside my home and some houses near me have these green lines painted on the sidewalk. I thought maybe this is a new form of chalking but there’s nothing on our tires and we have a permit.

I know that green can indicate sewer utility below, so I called the city to see but I just got a “not sure try this desk” kind of game.

Any ideas?

Images: https://imgur.com/a/3mOcTEn