goldfish are not always one color because they have different species. Also, goldfish can change colors over time. They won't always be gold or maybe they won't always be white or whatever color your goldfish is.
The goldfish did not evolve naturally and in nature. Goldfish did however evolve with the assistance of man who selectively bred and developed them to have the different colours and shapes they now have.
Goldfish come in many different colours. They can be orange, like you normally think of, white, black, blue,silver or any combination.
It is quite possible that the black spot is part of the fishes colouration. Goldfish often have many different colours in many different shapes and shades anywhere on their bodies or fins.
You could go by the golden rule. If to all intents and purposes it looks and behaves like a goldfish, in all probability it is a goldfish. Goldfish come in very many different shapes, sizes and colours.
They were bred that way.
it is called a comet chameleon because it can change colours to the different colours in the comet
They start off as uncoloured fry and as they grow and develop, their colours also develop until they are fully coloured.
Goldfish is simply the common name given to a species of domesticated Carp. They have been bred to be of many colours and body and fin shapes and many of these "Goldfish" have other names too which defines their different colours and shapes..
Goldfish are a variety of colours from white, black, orange, red, blue-like tinges, and even browns
I think baby goldfish are called fry.
Different sized stars burn at different temperatures. Different temperatures produce different colours. Stars that are moving away from us will shift their colours towards the red. This is called "Red shift".
It looks like a common carp but it has bright colours that may be any combination or single colours ranging from Blueish to White or Gold.