Also have Comets. Congrats on your first eggs. As the other posters have said, yes, the eggs start small and get larger as the Comet's "plumbing" gets used to the process. Relative to body size, my Comets lay the largest eggs in my flock. (Duck eggs are larger still, but so are my Pekin ducks).
Color is definitely diet influenced, with successful free ranging generally resulting in more orange-toned yolks. Moreover, if you are fortunate enough to be able to let your flock free range, and have a varied diet available to them of growing green things, you will likely find that different birds, different breeds, will have differing green favorites. An example from my own situation:
Though I made no change in feed, as we came into the fall, something on my property was suddenly attractive to the ducks (and only, seemingly, the ducks). They ate so much of it their yolks took on a green tinge for a couple weeks, while the rest of the flock's yolks were (mostly) unchanged. It being our first year of raising them, we were so nervous we stopped eating them till we could look it up and compare what we were seeing with the various common causes of "green eggs" on the internet. I then confirmed that by butchering a duck and a chicken almost back to back. The duck's crop was jammed full of a particular green grass on my property, while the chicken (whose crop was also full) had essentially none of that particular grass, but plenty of other varieties.
Hope that helps!
