My all time favorite crane (do I have another favorite though the container cranes at the Port of Miami are lit up with festive lighting which is awesome http://luxpopuli.com/New/wp-content/uploads/2016/11/miami-view-with-cranes.jpg ) was the crane that glowed after dark for all of us to see atop 1 Dalton! So beautiful at night, it grabbed our attention, focused us on this new emerging tower! I so wish other construction companies would do the same with their cranes. Imagine the Seaport if all their cranes were lit up in color. Such a sight it would be!
Not sure, but in the past I have seen them used to advertise the crane rental company or the projects General Contractor. With the recent high winds I would suspect they would be a danger to the crane operator. Could they be some kind of locator device?