There's a reason why 'sky blue' lights are used to honor 9/11 victims

(NEXSTAR) – The National 9/11 Museum & Memorial, which is marking the 25 anniversary of the attacks this year, maintains a special place for “sky blue.” In recent years, the 9/11 Museum & Memorial has encouraged buildings across New York City to light up their rooftops or facades in remembrance of those who were killed [...]