"Isabel" genetically is Lavender diluted Crele. Crele is Cuckoo/Barred Partridge. Lavender, is Lavender. It is it's own gene and is sometimes also referred to as Self-Blue.
The reason Isabel "looks to be just a lavender with tan/gold leakage on the hackle, saddle, and shoulder feathers??" is because Lavender doesn't only dilute the black based parts of a birds plumage but also the red/orange parts of the feathers. So the black barring turns pale gray (Lavender) and the red/orange of a Partridge bird turns yellow/pale gold.
The pastel hue of the Isabel color makes it hard to discern the bird's pattern. Conversely, depending on how well patterned underneath the Lavender dilution is could attribute to the lack of definition in the bird.
Breeding a Black cock bird to a Isabel hen will produce single barred male offspring and solid Black female offspring. All with red/gold leakage (especially in the males) and all recessively carrying 1 copy of the Lavender gene.
Breeding a Isabel cock bird to a Black hen will produce single barred male offspring and barred female offspring. All again with red/gold leakage and all recessively carrying 1 copy of the Lavender gene.
I guess I'm gonna be in the market for English Lavender/Self Blues soon.
Thanks Jeremy, it all makes more sense when you see it in writing
