Celebrities around the social-media sphere donned their brightest orange Tuesday to participate in the “Wear Orange” campaign, part of the first-ever National Gun Violence Awareness Day.

Julianne Moore, Piers Morgan and Jason Bateman were among countless stars and organizations to tweet photos of themselves or family members wearing bright orange clothing. “Wear Orange” was inspired by a group of Chicago teens who asked classmates to commemorate the life of 15-year-old Hadiya Pendleton, who was shot and killed one week after marching in President Obama’s second inaugural parade in 2013. Pendleton would have turned 18 on Tuesday.

The color is meant to echo what hunters wear to protect themselves in the woods.

By coincidence, the campaign comes just a day after a British GQ interview with Vince Vaughn (“Wedding Crashers,” “Anchorman”) generated some controversy as he expressed his support for gun rights, saying he supports guns in schools to prevent mass shootings.

“I support people having a gun in public full stop, not just in your home,” Vaughn said. “We have the right to bear arms to resist the supreme power of a corrupt and abusive government.”

Others participating in the “Wear Orange” campaign include Melissa Joan Hart, Susan Sarandon, the New York Mets and Sen. Elizabeth Warren (D-Mass.). MTV’s on-air logo was colored orange to mark the day.