Willie Mathews from South-Africa reported us that, after he bred the first *orange* Agapornis fischeri in 2015, he now can confirm that this phenotype is indeed caused by an autosomal recessive mutation. He paired that *orange* bird with normal greens. Later he paired the youngster of these pairs and in the offspring, there were, as we can expect from an autosomal recessive inheritance, *orange* birds. This year (2023) he paired up 2 orange birds and they have all *orange* chicks in nest.
To be clear: these birds have, as far as Willie could trace back, no link with the dun fallow bloodlines.
Read more about it: Red lovebirds, a mutation?