I'll see about getting into this more when I have time.
The last couple look like or if not close enough to exchequers. I would just go buy some instead of trying to build them. Ive work with them quite a bit and the info out there is limited or not in agreement or doesn't match what ive experienced.
In my experience exchequer is not simple mottling bred to that extreme. And I don't know if I believe its just a different type of mottling.
In my experience you can't make the pattern without having it in a starter bird.
The first bird is a blue gold duckwing. I saw that pic about 6 or so years ago and decided I'm making one of those.
The process is easy the execution is almost impossible especially if you want to use only leghorn blood. The US doesn't have leghorns that carry blue. We both saw the hatchery that offered them but they have since discontinued so IDK if they even sold any or if they were really leghorns.
I once heard someone pulled blue from a white leghorn but I can't confirm that.
I looked for two hears for any leghorn with the blje gene and never found any.
Depending what you could get it isn't hard to do. Breed whatever has the blue to a light brown then breed blue offspring back to browns until you get the duckwing pattern locked in and any unwanted bred out.
I started with a solid blue and bred it to a light brown. But of course that was to easy so I switched the next year and bred back to a silver duckwing and a cuckoo. I'm looking to end up with solid blues, cuckoo blues, and both blue gold and blue silver duckwings.
I'm just catching up on this thread and I know this post is months old, but it was me. I hatched blue birds out of a California White hen, father unknown. One wild little blue hen that stole nests everywhere and hatched out scores of chicks, most blue patterned. All her offspring laid like commercial birds the first year and were as broody as games the 2nd. I've been doing my best to keep the line going - the bird in my profile pic is a lemon blue from that line. I currently have two roosters that look exactly like what @MIAMI LEGHORN posted - blue gold duckwings.
Sadly, those two roosters and a lemon blue hen are the very last ones I have of that line, and at this point, due to outcrossing, they lay a creamy to very light brown egg. I would love, LOVE to get a bunch of Leghorns to put those roosters over, but I rent my farm, so can't build an official chicken coop, and the predators here are intense. I would give one of those roosters to someone who wanted to work on blue leghorns, although they're not terribly typey - I'll try to get pics soon.
If someone wanted to hunt up a blue gene in Leghorns, they might try California Whites, as the dominant white gene may be covering a surprise.