Grigioperla x splash

Si is possible that a grigioperla is carrier of a white-allel.
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.

BUT when : E/E lav/lav c/c phenotype is white.
Also when : eb/eb lav/lav c/c phenotype is white.

This because (in principe) recessive white "c/c" is EPISTASIS over ALL colorations !