From what I have read... Hmong is a term referring to certain people in isolated mountain villages from southeast asia... they keep chickens that are dark skinned (fibro) and there is a great deal of variation in feather color but body form is pretty uniform... when the immigrated to the USA and other areas they brought their chickens with them. Chickens are very important is some of their rituals (marriage, health etc.) Some folks in the USA perhaps elsewhere have been recently segregating colors to create color lines from the diverse flock so to speak.
interesting there is a member here who has posted about the rituals and importance of the chicken to the Hmong people... it is fascinating..
https://www.backyardchickens.com/threads/sacrificing-chickens-the-truth.409724/