What you notice walking across the I-5 overpass on NE 45th is that someone has systematically applied paint splotches to the top of each metal balustrade, and given the eight lanes of traffic humming along below, there are quite a few metal posts. Each splotch is about the same size and shape. Some are green, others blue like this one.
What you also notice is that when you stop to take a photo of the splotches, drivers above and below start nervously braking and looking at you: Is she a terrorist? What's she doing taking pictures of a bridge? Is she going to jump?