The Red Hat sects are the sects in Tibetan Buddhism.[1] They are named for the colour of the monks' hats at formal occasions, includes the three oldest of the four main schools of Tibetan Buddhism, namely Nyingma, Sakya and Kagyu.
The fourth school is Gelug and is known as the Yellow Hat sect.
A minority consider only the eldest school, the Nyingma school, to be the Red Hat sect.
. Melvyn C. Goldstein. Melvyn Goldstein. A History of Modern Tibet, 1913-1951: The Demise of the Lamaist State. 15 November 2023. University of California Press. 978-0-52-091176-5. 1.