Magpies - Which kits to keep from Chin doe?

[Nello'sHops&Lops]

I have a Chinchilla (Flemish) doe that was bred to a blue (Flemish) buck that is not mine. My end goal is to breed magpies. I have a harlequin buck (not Flemish), and I want to keep a couple of the kits from the (Flemish) litter with the blue.

I'm pretty sure I have the following colors:
Black Chin (not sure - I've been told my doe is blue chin but there's 2 babies that look like a darker chin and two that are much lighter)
Blue Chin
Self Chin
Chestnut maybe? weird mottled coloring that I think has cchl involved.

Is there co-dominance with the cchd gene? a few of them look a lot like a blue self, but have very mild chin-like stripey patterns on their fur. It would be nice to think they're harlequenized but I don't imagine they are.

There are 9 kits. I only have space to keep 2-3, not old enough yet to see who is boys and girls anyways but that will help narrow it down too.

I'm assuming a self chin would be best for a magpie breeding program so that the ej has an easier time showing up, but can I confirm if that's what any of the ones that look blue are before a test breeding? I just cant keep 9 Flemish Giants for a year until they're all ready to test breed lol.