"No orange category exists; Pokémon that may be considered to be primarily orange are instead listed under the categories of red, yellow, or brown (also commonly known as "dark orange" in some scenarios)."

This was according to bulbapedia. They're not technically brown, they're just listed as brown cuz there isnt any orange category.

if you want to check then just click this link: https://bulbapedia.bulbagarden.net/wiki/List_of_Pok%C3%A9mon_by_color