Any idea what this EE Roo is mixed with?

[Blooms&Brood]

Chick hatched 12/18 from Meyer.

First profile pic is at 7wks. The rest of pics at 8, almost 9 wks. I haven't considered breeding, but if I was to keep him with my hens (California Whites, Australorps, Welsummers, Barred Rocks, and SLW) what should I expect from hatchlings and potential egg colors from hatched pullets? He intrigues me enough to ask for your advice! He has a fabulous shimmer in his feathering that I couldn't catch well in my lighting at night but is very similar to an Australorp.

 

[Little Chicken Girl]

The egg color of the female offspring are not very determinable unless you know the rooster's parents. Other than that, this is all I know...

Beard/muffed crosses usually result in bearded/muffed chicks (the bearded/muffed genes are pretty strong).
Since he looks like a partridge color variation, if you crossed him with the barred rock hen, you will likely get barred/Crele offspring.
Australorps have a strong dark eye color trait so australorp crosses usually end up with dark eyes.
Most Wyandotte/EE crosses I have encountered and seen have rose or pea combs, at least some degree of lacing and a wyandotte facial structure with a beard/muffs (wyandotte crosses often pass on the facial features).
Crossing him with a welsummer (if it is a partridge welsummer hen) will almost forsuredly result in partridge colored chicks (no guarantee though since his parentage is unknown). If he has blue egg genes, crossing him with a chocolate egg layer (like welsummer) will likely result in olive-egger offspring. However, there is no real way to determine what egg color genes he has, of course.

In all, it is pretty iffy... Hatching crossbreeds is not very determinable or guarenteeable... However, that is part of what makes it fun!
Hatching cross breed eggs are always little surprises! I bet whatever you end up with if you breed him with will be pretty though. He is a gorgeous little dude! I can see the shimmer even in that lighting.

 

[lomine]

If he is from Meyer his parents were more than likely both EE and his grandparents were EEs and so on. Colorwise you can’t really know what’s hiding in his genes.

You won’t really know what kind of egg genes he has until his daughters lay eggs. There is a very good chance that he has at least one blue egg gene because people want colorful eggs from EEs so the hatcheries want to keep those blue egg genes in their flock. Combine blue egg gene with brown and you get green. Combine blue and white you get blue. The genes for brown are a bit more complicated and beyond my knowledge of genetics.

 

[lazy gardener]

Chick hatched 12/18 from Meyer.

If I was to keep him with my hens (California Whites, Australorps, Welsummers, Barred Rocks, and SLW) what should I expect from hatchlings and potential egg colors from hatched pullets? He intrigues me enough to ask for your advice! He has a fabulous shimmer in his feathering that I couldn't catch well in my lighting at night but is very similar to an Australorp.

Crossing with your PBR will result in loose pea combed black sex linked birds which will lay either brown or aqua/green/olive colored eggs.

Crossing with your SLW should result in brown sex linked chicks with walnut comb. Their egg color would be similar to the BSL.

Check out this thread. There are some nice charts in the first post about the different birds you can cross to create your own sex links.

https://www.backyardchickens.com/threads/sex-linked-information.261208/page-181#post-15872144

As for the CW, lorpes, and wellies, I can't venture a guess.