Geneticly they are nown as cordovan type.
Cordovan shows up from time to time in all bee types. Its is a recessive gene for colour and is used as a marker in some breeding operations (Sue Cobey used to use it way back in the dim and distant), and acually is a melanin (black) deficiency.
We see it here occasionally in an otherwise dark colony where some of the bees are of a chocolate colour, the brown phase being where the black would normally be. In these cases everything that would be black is brown. It is most obvious in the drones if the queen is carrying any of this recessive gene, as a proportion of the drones carry the marker, and appear chocolate colour whilst the others remain black, and if none of the drones the queen mates to are cordovan the no workers will show that trait, it only showing up in the drones. Have seen it in bees of every hue, and yellow bees carrying cordovan are very light looking as even the legs and tips of the abdomen are merely milk chocolate coloured.
To get a handle on how common this is you have to bear in mind we have closing in on 3000 colonies and maybe see this in no more than 10 in any one year, so the normal small scale beekeeper may go his whole life and never encounter it. It is MUCH more common in certain lines (often of US/Hawaiian origin of Italian type bees).
Bees carrying visible cordovan colouration have a very poor reputation as honey getters. Because of their interesting colour Sue Cobey used to market them as 'red' bees and sold them for use in observation hives as something interesting.
We see all manner of odd things that others will never encounter.
A couple of examples would be.........
Extreme melanistic forms, especially in the drones, where even the wings are getting dark and the hairs intense black. Widespread anywhere there has been Caucasian genetica incorporated.
Drones with odd, sometimes VERY odd, eye colours. Last season we have had the following:- chocolate, chestnut, red, green, olive, yellow, and white. Most are just a few drones, but in the case of the green and yellow ones it is about half the drones in the hive, and they drift too. Only a couple of colonies, but really do look like bees from another planet, and their appearance in other colonies gives a good idea of drone drift, and it is surprising how far they go and how many other colonies they are in. See the odd one turning up in other hive groups from the original apiary, even a couple of miles away. As one might expect, usually in hives with a VQ either running or soon to be so.