The bigger chick in my avatar is my Olive Egger, and she has a teeny crest, so I'm going to go from there. I only hatched two olive eggers out the 9 eggs I got ( and the other one was a male). So, right now I only have her to start with.
I'm thinking of breeding a Polish hen to a blue egg layer, hopefully Araucana, (I absolutely adore the Araucana, but I've had so much trouble finding eggs right now). Hopefully, that will produce a crested chicken that lays a light blue egg. Then breed that one back to a dark egg layer. I have some Cuckoo Marans, but I don't really like the cuckoo color. I just sold my Welsummers, but now I wish I hadn't, as I just found out that a partridge bred to a blue would produce sex-linked chicks. I think I want to get some other color of Marans, maybe Black Copper or Birchen. Then pair the offspring of that second breeding, which should be an OE, to my wee-crested OE. I want to eventually get a Crested OE that will 'breed true', so to speak. I've been looking up information about OEs, and I'm still not sure if OE to OE is more or less likely to lay an olive colored egg. I've been trying to find a picture of the mystical "Avocado" egg, but my attempts have been fruitless (pardon the lame pun XD) . I might toss in an Isbar, too. The Marans/Isbar (Marbars) OE eggs I've seen are amazing.
I want not only an Olive egg, but a particular appearance as well. I need to study chicken genetics to make a definite plan. It may not work, or it may take several attempts to get the look I want, but, heck, I have lots of time, and I thought it might be a fun project. I just decided to do this a few months ago, so don't have a plan set-in-stone and any advice or suggestions are welcome and helpful. Sorry, that was a whole lot of explaining when basically the answer is, "not sure yet". lol!