I read what little I could find on ki shusui, (ki means yellow) but learned that although this type of koi is rare, when it ocurred, it was often as a by-product of crossing a green koi called midori with other midori.
Midorigoi, a fish that sometimes makes ki shusui.
A midorigoi, or midori, is a cross of a standard shusui and a metallic yellow koi called "doitsu ogon."
So, this koi has both shusui and ogon genes. It made sense, therefore, if you crossed midori x midori, a yellow shusui could come this cross of koi.
The picture below is is one of my midorigoi. Her name is "Jade.