Only some Buddhist Monks wear yellow robes.
There are many Buddhist sects, and each one has different rules governing the color of their dress.
The Mahayanist monks of Vietnam wear brown, the Theravada monks wear dark saffron or yellow.
Confucius’s followers were told to wear primary colors like yellow, blue, white, black, and red, rather than “intermediate” colors, such as purple or brownish tones. Although red was approved, Confucius personally felt red was for women only.
Taoist monks traditionally opt for yellow robes, following the old Yellow Turban movement of the third century:
Priests and missionaries wore yellow robes, and their followers wore yellow turbans simply to distinguish themselves as Taoists.
Alternately, Japanese Shinto priests are limited to only wearing white, light blue, or purple, depending on their rank.