I saw the post you made over in 'the land of the lost' about kigoi and chagoi. It actually isn't far off base for a joke, actually. The chagoi is not as old as the kigoi and although it looks like an early magoi direct descendent, it actually was not 'made' until 1910. This fish came from magoi, asagi and doitsu goi.
The kigoi would go back further than that. But there was a time when kigoi and chagoi were crossed regularly. This was also done with benigoi.
So the tea colored chagoi ( really any shades of brown and another color) gave way to a mustard colored chagoi ( from kigoi) and a choclate colored chagoi ( from benigoi). But the yellow of chagoi is densier due to the melanin being reintroduced into the yellow. So our eyes see more of a muddy mustard color.
And since all roads in our conversation lead to OCHIBA, it should come as no surprise to you that these chagoi are the ancestors of the early OCHIBA SHIGURE!

JR