Neither blue nor lavender, what is this gene?

[AlvinXsu-KMG]

This is the first documented case.

That's great. Compared with the dominant, the recessive needs double time. I think it will make up for lavender.
Also, sir, in this case, it should not dilute the red and buff?

 

[AlvinXsu-KMG]

I would guess a shade of blue, below I have been told she is blue splash...
View attachment 3324615
I have a different hen not related, who is pretty, I call it silver though...
View attachment 3324617

I think the second is true lavender.

 

[nicalandia]

That's great. Compared with the dominant, the recessive needs double time. I think it will make up for lavender.
Also, sir, in this case, it should not dilute the red and buff?

Two copies of the same mutation(Dominant Platium I^p/I^p) would produce an all white bird without a doubt.

Looking at the original hen, her gold tones were diluted so this mutation does dilute the color gold. You are not seeing this on your current birds because they are basically all black under the platinum. You can try with other color pattern.

 

[Poultrybonkers]

They look light blue to me I have one of each, a black, blue and lavender here they are together

 

[nicalandia]

They look light blue to me I have one of each, a black, blue and lavender here they are together

Some people very keen eyes when it comes to genetic mutations, the poster provided not only a single specimen of the bird in question, offspring of consecutive back cross to self black birds(WC Black Polish), The offspring show remarkably homogeneous expression.

 

[Egghead_Jr]

Why would you not conclude that the Cock carried Lav?
F1 would be half Lavender
F1BC would be half Lavender

OP does not state what happened in second generation, goes on with white tails instead. I'm assuming the same results of half the population produced was Lavender.

 

[AlvinXsu-KMG]

Why would you not conclude that the Cock carried Lav?
F1 would be half Lavender
F1BC would be half Lavender

OP does not state what happened in second generation, goes on with white tails instead. I'm assuming the same results of half the population produced was Lavender.

Because WCB has no lavender color in my country. I think there are few lavender colored Polish in the world. And I don't use the same male.

 

[JacinLarkwell]

Light Blue when crossed to solid black tend to get darker and not lighter

But dark blue to black can make light, so surely light blue to black can also make light

 

[nicalandia]

But dark blue to black can make light, so surely light blue to black can also make light

That is not how it works, by crossing back to black you gain melanizers, you don't lose them.

Have you ever heard about blue breeders breeding back to black lines to regain some of the shade lost by crossing blue x blue?

 

[nicalandia]

Because WCB has no lavender color in my country. I think there are few lavender colored Polish in the world. And I don't use the same male.

I agree, very few Lavender in the Polish lines.