From the USA Wrestling Officials Association
1. A singlet worn by a competitor needs to be predominantly red or blue. Often times our officials say that a singlet has to be a certain percentage red or blue (60% is the number I hear most often), but this is not in the rule book. Predominantly means the most common, main, or prevalent.
2. A singlet at regional and national competition can be either high cut or low cut. Only at the USAW Senior World Team Trials must an athlete wear a high cut singlet.
3. During freestyle and Greco-Roman competition, a two-piece singlet is not allowed. A two-piece singlet is, however, allowed at USAW folkstyle events, provided the top is tight fitting and the shorts are either compression shorts or board shorts. The shorts shall not be excessively baggy and shall not have pockets, buttons, or snaps.
4. All female competitors must wear a women’s cut singlet.
5. At Cadet & Junior Nationals, competitors must wear a state-approved singlet.