So there I was, leaning over the red paint splotch, trying to decide just how much (if any) of the lighter-grey sidewalk to include in my super-minimalist shot, when a random passerby said "Hang on, let me help!" and dropped to the ground. I played along, thinking "actually, that's kind of the opposite of helpful", and snapped a bunch of shots of Random Photographer Sprawled On The Sidewalk before he bounced back up and we all moved on.

Two blocks later, I got it...

(and this one totally worked better than my original shot (see note). thanks, RandomGuy! :D )