Grigioperla x splash

Look Rachele, is not soo difficult the genetics (when you breed within the same groundcolor family and when that groundcolor is pure , means 2 exact alleles as E/E or eb/eb or eWh/eWh) !

when you breed whit 2 grigioperla that have a genoom :
E/E lav/lav C+/c X E/E lav/lav C+/c
(as you can see they are both "pure" grigioperla in phenotype but are also both carrier of ONE c-allel)
The result is, as Tünde say, +-25% white and 75% grigioperla.
Why?
Because when come together the c-allel of the father and the c-allel of the mother these become "epistasis" over the E/E and over the lav/lav, so a recessive white phenotype E/E lav/lav c/c .
The rest will be +-25% grigioperla phenotypes E/E lav/lav C+/C+ (not carrier of c-allel).
and +-50% grigioperla phenotypes E/E lav/lav C+/c (carrier of 1 c-allel).

ALL THIS IS GOOD IN THEORY WHEN ALL BREEDING PARENTS ARE "PURE" !
BUT LOOK THIS (when the ground color become NOT more pure as E/eb) :
You breed a "pure" grigiopela E/E lav/lav X a "pure" white eb/eb c/c and you result in "UNPURE" groundcolor for the chicks E/eb Lav+/lav C+/c these are "unpure Black" phenotypes carrier of 1 lav-allel and carrier of 1 c-allel. BUT the black will not be "pure" black (they will show more or less gold (or Silver) in there necks, shoulders, wings ...) Remember your crosses you did 2 years ago Rachele.

When you now cross these brother X sister E/eb Lav+/lav C+/c you will become 128 different genotypes and in 5 different colored phenotypes (which all can look a little different because of there little different genooms) :
-lavender patterned isabel partridge;
-black patterned gold partridge;
-black;
-grigioperla;
-white.
You understand from now on it will become impossible to predict what the future outcomes will be !!!!!