In Japan, graduation and matriculation ceremonies take place in March and April. These are formal, celebratory occasions and there are certain rules of ettiquette when attending as a parent or guardian. Be sure to turn your phone off or put it on silent mode before the ceremony begins. Also, do not wear clothing that is too flashy. The most important people in the ceremony are the children, so the parents do not have to show off.
For graduation ceremonies, black or navy is common, and for matriculations navy or grey are common. As much as possible it is a good idea to wear formal clothing.
Avoiding excessive jewelry is also recommended and wearing only necessary rings (e.g. wedding ring) is seen as the most fashionable.