Wiktionary
yellow state
n. (context US idiomatic English) A state of the United States where the Libertarian Party is influential.
Usage examples of "yellow state".
The two divers unloaded their tanks and masks in the back of a yellow state truck and prepared to ge~as well.
Shad circled the Flesh Farm until he spotted the health inspector's car, a gray Dodge Aries with yellow state plates.