The robes were enchanted to grow as their wearer did, and also to change colour to indicate the wearer's scholastic progress, starting off pale pink and ending up gold if top marks were achieved in every subject.
When a student broke the International Statute of Wizarding Secrecy, or betrayed the Japanese wizard's code by practising Dark Magic, the uniform turned white. This was considered a huge disgrace, and the student in question would immediately be expelled, and would face a trial with the Japanese Ministry of Magic.
Behind the scenes
- In Japanese culture, cherry blossoms (sp. Prunus serrulata, the "Japanese cherry"; in Japanese 桜 or 櫻; さくら sakura) in shoujo manga or anime symbolise youth and innocence. Also, the blossoming of the cherry blossom trees coincides with the start of the Japanese school year (in many parts of Honshū). These would explain why beginner students' robes are pink: the colour of cherry blossoms may range from white to the more familiar pink hue, and as Mahoutokoro is part of the administrative vicinity of Honshū (where many school and public buildings have cherry blossom trees planted outside of them), cherry blossoms begin blooming by April, the same time the fiscal & school year starts.
- In Asian culture, the colour gold (金 きん kin) which was interchangeable with yellow (黃 き ki), was reserved for and symbolised/represented the Emperor.
- In the case of yellow, in Chinese culture, it is the colour of happiness, glory, and wisdom; as well as symbolising the middle direction of the Chinese-oriented compass. These may be the reason why the robes turn gold if the student earns top marks in every subject.
- In Asian culture (specifically East Asian, where Japan is part of), white is mostly the colour of death, mourning & funerals. Both the deceased's shroud and the mourners' clothing are of undyed white linen, and during the days of mourning, white flowers (either paper, or chrysanthemums) are piled up by the area of the coffin; these may be the reason why the robes turned white when the wearer practised Dark Magic.
- The way the robes change colour as the students grades go up could be a nod to the belt system in martial arts. Where when a participant gains experience, the move higher up in the system.