I've wondered the same thing TV. I have several pairs of Goldens and thought about puting an extra red hen with a yellow rooster but wasn't sure if it would mess up the genetics. I'm not up on the details of golden pheasant color mutation genetics. I suspect the offspring would be primarily reds carrying a recessive gene for yellow that would only show itself if mated to another red individual carrying the same yellow gene. I wouldn't hold my breath expecting to get an orange or orange-yellow bird, but I too would like to hear if anyone has any experience with this.
That's what I was thinking, that the chicks would all be red unless the hen also had yellow in her genetic makeup. Then mating 2 siblings together would produce both red and yellow. I don't know for sure if it works that way with these birds; has someone done this?