The symbolism in the academic regalia worn by graduates at Commencement dates back many centuries. Although some aspects of the costume vary among academic institutions, many basic elements are similar. The cap or mortarboard is based on the medieval biretta worn by scholars and artists. The gown's cut and velvet trimming indicate academic rank. The doctoral hood may display the academic field of the wearer's degree and the institution from which it was received. In addition, tassels, cords, and medallions denote various honors awarded by the institution or academic societies.
At Commencement, the assortment of colors in academic regalia is on full display. Faculty members are adorned in robes, the colors of which correspond to the scholar's alma mater. However, at the time of graduation, most PhD recipients are draped in doctoral hoods that are trimmed in blue velvet, signifying a doctor of philosophy degree, and lined in the colors of the institution conferring the degree.
Caltech graduates receiving a doctorate wear Caltech's signature blue velvet cap, robes trimmed in blue velvet, and a blue velvet doctoral hood lined in a chevron pattern of orange and white. Those receiving a bachelor's or master's degree wear a simple black gown and a black mortarboard or cap.
In addition to these traditional items, an undergraduate may also choose to wear a colored stole to the graduation ceremony. While orange stoles denote Caltech pride, other colors may be chosen to represent the undergraduate's residential affiliation.
There are currently eight undergraduate houses at Caltech—Avery, Blacker, Dabney, Fleming, Lloyd, Page, Ricketts, and Ruddock—and three undergraduate residences, Bechtel, Marks, and Braun.
- A white stole or a purple and white tassel designates Avery House; Avery's house color is white.
- The students of the Bechtel, Marks, and Braun residences who affiliate with a house may choose to wear that house's tassel or stole.
- A silver stole or a black and white tassel designates Blacker House; Blacker's house color is black.
- A green stole or tassel designates Dabney House; Dabney's house color is green.
- A red stole or tassel designates Fleming House; Fleming's house color is red.
- A gold stole or a yellow and white tassel designates Lloyd House; Lloyd's house color is gold.
- A blue stole or tassel designates Page House; Page's house color is blue.
- A maroon stole or tassel designates Ricketts House; Ricketts's house color is maroon.
- A navy blue stole or tassel designates Ruddock House; Ruddock's house color is navy blue.
Caltech's PhD regalia