How in the world did these chicks have these colors?

[ColtHandorf]

Huh, Mauve Splash comes to mind seeing them fully feathered out, but I'm not sure that's quite right either.

 

[britesidefarm]

Update: the cockerel is now fully feathered

And we ended up having some accidental chicks hatching at the moment, most likely fathered by him. One already hatched who I’m 100% sure is his. (Note the lavender/mauve spots)

 

[RoostersAreAwesome]

Update: the cockerel is now fully featheredView attachment 2662882
And we ended up having some accidental chicks hatching at the moment, most likely fathered by him. One already hatched who I’m 100% sure is his. (Note the lavender/mauve spots)View attachment 2662886View attachment 2662887

He really looks like a dun or khaki. I think I have a possible theory on how he and his siblings got their coloring. Polish are one of the the few breeds that come in dun/khaki without it being super rare. However, it it still uncommon. But I can’t think of any other explanation.
Since your rooster is a polish mix, it’s possible he has it. Dun/khaki is a dilution of black, so dominant white (which both the grandfather and father appear to have) would hide it.
Actually, this theory is probably completely off, seeing as the rooster has a white tail... which would mean he has dominant white? But dun and dom white can’t visually coexist, since dominant white covers any dilution of black. Yet he also appears to be silver due to the white wing triangle.
Looking at my rooster, he had a brown tail. I don’t think there’s a way for a chicken to have a tail that is completely white because of silver.

 

[Amer]

Update: the cockerel is now fully featheredView attachment 2662882
And we ended up having some accidental chicks hatching at the moment, most likely fathered by him. One already hatched who I’m 100% sure is his. (Note the lavender/mauve spots)View attachment 2662886View attachment 2662887

To me he looks like lavender barred with golden leakage (which would turn the lavender brown) but I can’t explain the white tail.

 

[Bird fanatic]

Update: the cockerel is now fully featheredView attachment 2662882
And we ended up having some accidental chicks hatching at the moment, most likely fathered by him. One already hatched who I’m 100% sure is his. (Note the lavender/mauve spots)View attachment 2662886View attachment 2662887

Wow he is beautiful I have never see a chicken with that coloring!!