I have crossed Marans with Barred Rocks and Buff Orpingtons, I used a blue copper roo and a splash copper roo. The egg color does darken in the offsping produced. I would say I get probably about a 4.5-5 on the color chart. The barred offspring from that cross came out solid blue and they have the body of a BR, short and sqwuatty, but got the fluffiness of the Marans. The Buff cross offspring are large like buffs and were better layers than the BR crosses. The BR crosses were terrible layers and the eggs were so big and round that I think they had issues laying, I have one of these birds left from those test crosses and she is a BR cross Splash Marans.....she might lay 6-10 eggs per month. When she does lay it is a beautiful egg, no gloss and very big with stress cracks all the way around the equatorial band. The nice thing about the BR cross is that they came out sex-linked, so I could cull the roosters sooner rather than later, their butts were so fluffy, I had to and have to keep the remaining gals rears clipped down to almost no feathers, messy messy messy. Due to the difficulty of laying and the inconsistant laying pattern with the BR cross, I will not cross these 2 particular breeds again. The Buff crosses were good layers and nice big birds that also laid an egg between a 4.5-5 on the color chart, very mellow birds from this cross. A lady who came to pick up some pure Wellies and Marans from me decided that she wanted the Buff cross Marans birds (that weren't for sale) as she liked them better than the pure birds. Needless to say, she liked them sooooo much, she went home with them.