If you were strolling by the Hudson County waterfront Monday night, as we were, you may have noticed the Empire State Building lit up in more than its usual one or two-color scheme.

It had at least four colors going. And do you want to know why?

It's "tie-dye" to celebrate the upcoming Grateful Dead exhibit at the New York Historical Society, which will open in March of 2010, according to the New York Times.

Only thing missing from the building: A touch of gray.

(Photo taken from Hoboken waterfront, Sinatra Drive.)