Hi Mitch, OK, that makes more sense. The reference to Yamabuki is confusing albeit historically accurate. The better way to express that would be a hikari X normal .
Mike, ki utsuri most definitely exist in butter yellow. You are seeing 'baby ki utsuri' from hi utsuri ( more washed out versions of hi utsuri) and the orange naturally comes on as the fish grows and the skin gets wider showing more color cells. But ki utsuri is a luten gene that creates a pastel yellow- a common color gene in many animals.
So there is the true yellow utsuri, and the trouble is NOT the yellow- it is the sumi!! Really really poor quality sumi and sumi wrap formation.
In addition, the trend in these yellow utsuri quickly when towards metallic skin and the flat yellow utsuri was kinda left behind. You can still see them once in awhile. 5 or so years ago, Miyatora had a boast load of them and quite cheap?! Even for a guy who prices like Miyatora ( his hatred of white boys is legendary!!)
Here's a show winner for you---