I'm not sure if you're joking but the only reference I can find is the "Blue Dog Coalition" which takes its name from "being choked blue" and the term "yellow d

I'm not sure if you're joking but the only reference I can find is the "Blue Dog Coalition" which takes its name from "being choked blue" and the term "yellow dog Democrat", which in turn seems to refer to what now goes by "vote blue no matter who" in the sense of "they would vote for a yellow dog as long as it is Democrat", which in turn uses "yellow dog" to refer to "low value" American dogs with no genetic link to any established European dog breed. Whew, what a ride for a non-American to figure out what any of these idioms are supposed to mean.