Ah, I thought I saw it here....wikipedia is good stuff...
In 1162, the Empress of the Song Dynasty ordered the construction of a pond to collect the red and gold variety of those carp. By this time, people outside the imperial family were forbidden to keep goldfish of the gold (yellow) variety, yellow being the imperial color. This is probably the reason why there are more orange goldfish than yellow goldfish, even though the latter are genetically easier to breed.
Here is the link if anyone wants to read more...
http://en.wikipedia.org/wiki/Gold_fish#History