Question: why does aang have tattoos?
Answer: The Blue Arrow tattoos are traditional Air Nomad tattoos. Tenzin, like Aang has them because they are Air Monks, Korra doesn't because she's water tribe. ... When he masters Air Bending, he earns his tattoos. Even right out of the ice, Aang was a practiced Air Bender, hence him having the arrows at age 12.