Your wife has a sharp eye!
I don't layer, as a rule. Instead, I try to mix it before I shoot it.
Apple Barrel sells an opaque mossy green. I actually add a few drops of Createx trans. dark brown to get a little deeper green for my trout backs and shoulders. I thin with Windex or Createx trans base, because the Apple Barrel paint is thick.
For an Ayu color, baby bass to me, I do pearl white belly and sides, moss green upper sides, shoulders and back, then use straight trans dark brown on the back, and over the shoulders lightly.
I don't know how to get that hue in a truly transparent color, but I'd play around with a trans med green, trans yellow, trans brown, and maybe just a drop of black, if it's still too light. I think avocado when I'm mixing, and then, once I've gotten that color, I darken with the dark trans brown.
Let us know what you finally come up with.