(NEXSTAR) – The National 9/11 Museum & Memorial has 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 during the attacks on September 11. Specifically, the city’s iconic buildings will be illuminated in a striking sky blue — a color that holds special significance for the organization, and the city as a whole.

Sky blue, or “Memorial Blue” as the color is also referred to, symbolizes the city’s (and the world’s) general perception of the sky in the morning just prior to the attacks. In fact, the cloudless skies above NYC on 9/11 had been described as what pilots and meteorologists call “severe clear,” meaning visibility conditions were seemingly infinite, according to the National 9/11 Museum & Memorial.

This year, dozens of iconic buildings, landmarks and institutions will again be partaking in the “Tributes in Light” event, itself an extension of the longstanding (and perhaps more recognizable) “Tribute in Light” art installation in Lower Manhattan, which form two columns of white light shining up the heavens.

Sky blue, too, is also a prominent feature of one of the museum’s most visually arresting installations, titled “Trying to Remember the Color of the Sky on That September Morning.” Found inside museum’s Memorial Hall, the piece is comprised of 2,983 watercolor squares — representing each of the lives lost on Sept. 11 and the 1993 bombing at the World Trade Center — showcasing different hues of blue to symbolize our memories of the sky on the morning of September 11, 2001.

“Our own perception of the color blue might not be the same as that of another person,” the museum explains of the different hues in the piece, created by artist Spencer Finch. “However, just like our perception of color, our memories share a common point of reference.”

The Museum is also encouraging folks to “Remember the Sky” by sharing photos of the sky to social media on Sept. 11, to help ensure that younger generations never forget the significance of the date.

“Through creating a shared moment of active remembrance together, the 9/11 Memorial & Museum aims to help spur conversation on social media platforms and elsewhere that can serve as a bridge between memory and history for the tens of millions of young people who did not live through that day that changed our world forever,” the museum has written of the campaign.

Those wishing to learn more about the commemorations taking place on 9/11 can visit 911memorial.org for additional information.