Interesting. Get some babies and see if any look like her. If she turns out to be genetic and co-dominant no telling what the homozygous version would look like. On the other hand I've heard that cold incubated eggs might produce dark babies but the belly border stripe gives some more hope that simple genetic. Worth trying anyway, especially with a female.
Here is a dark girl I’m trying to breed back to one of her sons this year just in case even though I’m not overly optimistic about her being genetic.
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