yellow color in the Lý dynasty was tolerable since the Imperial clan wore red and white color. However, things changed at the beginning of the Nguyễn dynasty. Commoners now had a limited choice of similarly plain and simple clothes for every day use, as well as being limited in the colors they were allowed to use. For instance, commoners were not allowed to wear clothes with dyes other than black, brown or white (with the exception of special occasions such as festivals), but in actuality these rules could change often based upon the whims of the current ruler. The áo tràng vạt was a traditional cross-collared robe worn by Vietnamese before the 19th century. During the Nguyễn dynasty, it was replaced by the áo ngũ thân and became obsolete. The áo tứ thân or "four-part dress" is one such example of an ancient dress widely worn by commoner women, along with the áo yếm bodice which accompanied it. Peasants across the country also gradually came to wear silk pajama-like costumes, known as "áo cánh" in the north and áo bà ba in the south. The headgear differed from time to time. People of the Lý dynasty and Nguyễn dynasty often put on a plain piece of cloth wrapped around the head (generally called khăn đóng), while in Trần dynasty and Lê dynasty leaving the head bare was more common. Beside the popular nón lá (conical hat), a vast array of other hats and caps were available, constructed from numerous different types of materials, ranging from silk to bamboo and horse hair. Even the nón lá (conical hat) came in several different shapes and sizes, now only two styles still persist. For footwear peasants would often go barefoot, whereas sandals and shoes were reserved for the aristocracy and royalty. Nguyễn emperors had the exclusive right to wear the color gold, while nobles wore red or purple. In the past the situation was different, Đinh dynasty and Lý dynasty rulers wore red, and Trần dynasty emperors wore white. Each member of the royal court had an assortment of different formal gowns they would wear at a particular ceremony, or for a particular occasion. The rules governing the fashion of the royal court could change dynasty by dynasty, thus costumes of the Vietnamese court were quite diverse. However, certain fundamental concepts applied. The most popular and widely recognized Vietnamese national costume is the