That is what I assumed. Chinese zoos often display a variety of goldfish forms, many of which look quite unhealthy, but I've not seen this before or since.
There are several methods of dying fish. They can simply be dipped in dye (same as for clawed frogs etc) which gives them an all-over colour, or part-colour if only part of the animal is dipped. Second, they can be injected with dye. The third method is what I think is going on here, where the fish are literally painted.
There's a photo below which I took in a Chinese animal market, of clawed frogs which have been artifically coloured using the "dip the whole animal in dye" method.
@Great Argus - I don't know what sort of "paint" they use (it would obviously have to be something which sets almost immediately), but when painting it is actual painting - the fish is out of water and each scale or body-area is painted with a brush.
I don't know how common it is compared to injecting dyes (which is very common), but that's what the photo looks like to me.
Perhaps worth noting, painting is somewhat temporary (the paint wears off) whereas injecting dye is permanent. Dipping the entire animal in dye is probably also permanent or at least long-lasting, but I'd imagine the animal doesn't have a full lifespan after the dipping.
I actually owned a rescue terrapin that been 'painted'. I never worked out how it was done, clearly some some kind of automated process because of the nature of the design. He was given to a friend of mine for free when we visited a pet exhibition in a local mall and I adopted him. The paint went right over his face and sealed his eyes shut but a vet was able to get that part off. The shell covering I couldn't shift for months until natural growth finally forced it to crack.
With these fish there is something about the way each scale is coloured that makes me think dyeing is more likely. When I saw them in person I know that dyeing was my fear as well.
