It's odd to note that all of the above are female, so perhaps we look for this more? Dunno, maybe I should suggest this one to Sonya for a future psychology project. :)
Anyway, yes, the board is racist. I have yet to see white that isn't the color of the girls' skin, and the red dress and blue background is obviously intended to be the red and blue of the American Colors, which could lead to the conclusion that the White of America is, well, white people. I'm positive this was just a dumb advertising idea that somehow no one picked up on, but this billboard is hoisted right above the Hill District (one of the black communities in Pittsburgh), so I find it horribly offensive.
The first time I saw that, I blinked, the next time I looked for any other white (as Roni pointed out), and a few times after that I pulled out my camera to see if anyone else would see the same thing I did. Given that others did, I'll check to see if the billboard is up still tomorrow, and find the name of the museum, and then it's information online to see about complaining.
Thank you everyone who replied!