That variegated orb of light is an installation piece by artist Leo Villareal, currently on view in Madison Square Park through February.
According to the piece's website:
"Relying on LED technologies driven by chance, BUCKYBALL’s light sequences will create exuberant, random compositions of varied speed, color, opacity, and scale. BUCKYBALL will trigger neurological processes within the brain, calling on our natural impulse to identify patterns and gather meaning from our external environment."
Maybe. I dunno. I just thought it was kinda pretty.