Blue is an egg shell cllor and is dom. Meaning only one is necessary to make it blue however if they have the blue gene from both parents it is a deeper blue color.... Once you have your chick with the deepest blue you can get mate said chic to a dark brown egg layer.. Then keep mating thoes chicks back to a dark brown egg layer it is the brown coating on the blue shell that creates the green your seeking and it is successive breeding with the darkest brown layers that creates an olive color provided you began your program with the best blue you could find....(a chicken with 2 sets of the blue gene) also i just read some research done on the blue footed boobie studying the blue egg shells and the research team got the bird to lay a progressivly darker: egg as the laying cycle progressed it is typically the oppisite the egg color lightens up the further you go in a hens cycle... they were able to accomplish this with an increase in diet of caritines the anti-oxident so talked about in many dark orange and purple fruits and vegatables..... So my sugesstion would be to do all you can through breeding then supplament with lots of organic purple fruits and veg if your chickens will eat it... I hope this helped i have been doing alot of reasearch on the subject i am wanting to crate a utility breed of blue egg layers i think it woild be really cool!
