I am really facinated by the yellow chicks that have came out.
After thinking about this for a day and seeing all the clarifications and photos the only think that this reminds me of from things I have learned about from studying the Marans Breed is the resessive white gene.
One of the main lines of Black copper Marans in the USA was inmported with the resessive white gene. Yellow sports would pop out with the probablility of 1:300 in this line. At first people were culling the yellow chicks because they assume they were impure. Thom Dean (no relation) started collecting these sports and discoved that they had ressessive white. He created a beutiful flock of White Marans that were genetically Black Copper Marans. When they were breed back to unrelated Black Copper Marans all the offspring was the black copper coloring and the off-spring when on with the resessive gene in the line. However when the resessive White Marans were breed to another resessive White Marans all of the off spring came out white.
The resessive white is not a color pattern, but something that inhibated the formation of color in the feathers. Today these resesive white flocks are often refered to as mutant black copper marans or mutant self white marans.
If these Cream Legbars have the the same thing going on, then they may look line my CockinxSilkyx White Leghorn mix. White with a crest.
Also...the Golden Legbars don't have golden chick down. They look just like the cream legbars when they hatch with the females having the chipmonk striped and the boys coming out with blurred striping and white spots on their heads. I hatched a pair of "Golden Legbars" from a breeder in my area that has been working over 5 year on recreating the line from brown leghorns and barred Plymoth Rocks. The adults look just like a cream legbar only with out the cresting and gold colored hackels on the hens rather than cream color. Below is a photo of my "Golen Legbar" Pullet. I also pulled up photos of the Golden Legbars in the UK and they look the same.