I'm curious why it's there. Any thoughts? answers? (The pink coloring is a result of the flash/lighting.)
@bisco is correct. Put your fingers over it and watch your speedo get replaced by a silhouette of your fingers.
I thought the mystery was going to be why the Prius has a projected, mirrored combo meter display, when everybody else just sticks a regular display on the dash where you can see it, and calls it a day.