|The following is based on Fallout Shelter and some details might contradict canon.|
The barbershop is a room where dwellers can change their hairstyle, hair color and facial features. Each upgrade allows for small additional upgrades. Unlike other production rooms, the Barbershop is placed as one room that takes up two room spaces. Hair style and facial features are consistent from dweller to dweller, but hair color doesn't follow the same pattern. Grey hair can be color 1 for one dweller, but color 5 or 6 for another.
Facial Features include additions, such as hats or portions of outfits, such as the hockey mask from the Horror fan outfit. It is also possible to change a dweller into a Ghoul with the Features characteristic.
Level 1: 10,000 Level 2: 50,000
The barbershop has 2 levels to upgrade, much like other rooms. The first basic level only allows one to customize a Dweller's hair and hair color. The second upgrade which costs 50,000 caps, allows customization of a dwellers facial features including glasses, facial hair, and hats. It also changes the name of the room to "Salon".