Ciao Monica,
I searched for some articles of breeders of Marans.
Was very interesting about the coloration of the eggs.
Members of the Belgium Marans-club did a few experiments :
They did a cross between a
Leghorn cock (out of white eggs) X several
Marans hens (out of dark brown eggs) : their female descendants produced all
WHITE eggs.
Thet did a cross between a
Marans cock (out of dark brown eggs) X several
Leghorn hens (out of white eggs) : their female descendants produced all
BROWN eggs.
This proved the Marans cock indeed have a big influence on the coloration of the eggs. I hope I could give an answer to your question.
What I wrote here comes out of this article :
www.marans.be/NL/pages/ChrisEieren.htm
Ciao Danny.