Byeolgigun Army(별기군[別技軍])is the Joseon dynasty’s new style army established in 1881. Like the Ottoman Empire’s Nizam-ı Cedid Army, Byeolgigun was very different from the previous Joseon army. They used rifles(Remington Rolling Block and Snider–Enfield) instead of harquebus. And were given comfortable clothes, too. Plus, it was only aristocrats who were able to join this army.
 
I colorized this photo. It was taken in 1881, Seoul. Byeolgigun was famous for their green uniforms. Some people called ‘Green Army’ as their nickname.