Interesting! I thought I heard something like that.
Can you explain a bit further?
How does it work?
There's a sexlinked gene that either allows dark skin or blocks it. We mostly notice it in the legs, although it affects the other skin of the bird as well.
Being sexlinked, it works about the same as any other sexlinked gene.
The mother needs to have the dominant gene on her Z chromosome, so she can pass it to her sons. Light skin is the dominant. You can check by looking--yup, the hens have light legs.
The father needs to have the recessive on both of his Z chromosomes, so he passes them to both his daughters and his sons. Because it's recessive, if he has dark legs, then you know he's got two copies of the gene. Again, you can check by looking--yup, the male has dark legs.
So the daughters get their Z chromosome only from their father (W from their mother, no skin color genes there.) They have dark legs, like their dad.
The sons get one Z chromosome from each parent, so they get light from their mom and dark from their dad. Because light is dominant, they show light legs.
There are two good reasons it's not very common.
-- The dark legs sometimes take several weeks to be obvious, so it's not reliable at day-old (sometimes you can see the dark legs at hatch, sometimes not.)
--Certain feather-color genes also affect leg color. So black chickens tend to have dark legs no matter what skin color genes they've got, although you can sometimes tell by looking at the bottoms of their feet.
The gene is called "Inhibitor of Dermal Melanin," which is a fancy way of saying it blocks dark skin. Dermal has to do with skin, Melanin is the pigment that makes the skin dark. The usual abbreviation is Id. And there are really several variations of the dark ones (some are visible younger than others), but the one for light skin is dominant over all of the dark ones.