I'm from Poland... but I guess you asking where I live
I live in Thailand do when you happen to be on holiday one day you are more then welcome to visit me on my small farm
I think they call them here Mongol chicken I don't know why but I saw some Thai chicken keepers calling similar roosters like that - but theirs have usually red ish comb.
From what I undertstand, in Thailand, they have 3 different types of black meat chickens. There are ka dam phuphan, Yunnan silkies and black Mongolian. The Yunnan and black Mongolian looka similar and have straight combs and a body more similar to the layer type of chickens, while the ka dam phuphan has thai gamefowl influenced and are for the majority are pea comb and more gamefowl in phenotype.
The more reddish comb can be that they have less of the fibro-melonisis genes. Even yours trio with darker combs will produce some offspring with reddish/mulberry colored combs.
And since you're now living in Thailand, you have a better chance to obtain some really Indonesia ayam cemani. I've seen some nice ones on FB of ayam Cemani in Thailand. I think the majority of Cemani and other chicken farmers are in northern Thailand, like Chang Mai, Chang Rai,Nakhon and surrounding areas?