Two columns of light, one red and one blue, representing colours of Mitt Romney and Obama's parties respectively, had been winding their way up the skyscraper in a display put on by CNN.
Each column represented the number of electoral college votes secured by Obama and Romney.
As the channel projected that Obama would serve another term, the building was lit completely blue.
Using a brand new vertical LED-illuminated meter, the building displayed a tally of the dash to 270 electoral votes as CNN projected results from the 50 states.
The four sides of the 102-storey skyscraper were lit in red, white and blue, while two sides of its mast were lit in blue and two sides of its mast in red to show Obama and Romney's totals throughout the night.
The tower changes lights to recognise key milestones such as Christmas Day and Halloween.
CNN ran a test last Friday but no one worked out what the skyscraper was doing before today's announcement.
Thousands of Obama supporters, braving near-freezing temperatures, took to the streets in New York's Times Square chanting, "four more years!" and waving flags, ecstatically celebrated the victory.
The crowds shouted "Obama! Obama!" and motorists honked their horns as it became clear the Democratic incumbent had beaten Republican Mitt Romney to win a historic second term in the White House.
