If you aren't breeding these guys then the red in the wings is really not of any concern. If you keep on cockerel you will be tempted to breed them as some point though. Chickens are very addicting.
Yes...genetics play in to egg color. The Marans egg color is not an exact science though. Some people swear that the the egg color is sex-linked and inherited in the hen from the father only or recessive and only inherited if both the mother and the father have the same recessive gene. Early on I got a Dark BCM egg from a breeder that hatched with a dominate white color which could only have been fathered by a rooster from a dominate white variety that we suspected to be a white leghorn. While that hens didn't lay as dark as the pure Marans she did lay a darker egg than a Rhode Island Red or other brown egg layer proving that the dark egg genes are not all sex-linked and not all recessive. That hen was our best layer. She laid 275 Jumbo brown eggs. We liked her so much that we breed her one of our non-brown egg breed cockbirds and her daughter also laid eggs that were darker brown than a Rhode Island Red. On breeder who has been working with Marans for 12+ years and had Marans in every variety you can fiend told me that she has regained dark color in breeding line both from crosses to cockerels and crosses to hens. So it would appear that both the hens and the cockerel contribute equally to the dark egg color. The tricky part is that the cockerels don't lay eggs so it is more difficult to evaluate a cockerels contribution to the mix than the hens. To evaluate a cockerels contribution the most sound method is what is called progeny testing. Basically you pair a potential breeding cockerel with a hen with an established egg color (this can be a Marans hen, a light brown egg laying barred plymouth rock, etc.). They you grow out a test group of 5-6 pullets and when they start laying their are evaluation and calculation that are carried out to average the know dame's egg color with the egg color of each pullet and then to average the range of values from each pullet to assign a value to the cockerel. This is obviously a lot of work but well worth it in the long run. If you have 3-4 potential cockerels at 5-6 months old you can pair then with hens and 6-7 months later you can start evaluating their egg color numbers. If you have one that is contributing a #7 egg color to the offspring and two that are contributing a #5 your can cull the two that are contributing the #5 and at 12 months old you have a proven #7 cockerel to keep as your next breeding cock. By doing this you get better gains in the egg color. If you are just breed cockerels based on type you may go round and round in circles on the egg color with only marginal improvements. Now to make this more complicated I read an article by a German breeder and he said that he got hatching eggs and grew out pullets and when they started laying kept the ones that were laying the darkest eggs and sold the rest to a friend. His friend likewise kept the hens that were laying the darkest eggs and sold the rest to some one else. They following year this breeder visited the flock of the 3rd person and reported than the 3rd flock was producing offspring that laid much much darker eggs than his or his friends flock flock. So...like I said Marans egg color is not an exact science.
So...NO!!! Chicks don't typically lay the egg color that they hatch out of unless they are from breeding line that has been breed to closely related birds from the same breeding line for multiple generations to the point that every bird in the flock lays nearly identical egg color.
If two unrelated birds are breed together the out come can be very unpredictable and very wide ranges. I had old breeding line that the lady I got them from had breed for 5 years from one set of hatching eggs and the person that she got her stock from developed the line from one cockerel and one line of closely related hens. All the hens in that line a #6 egg at the beginning of their laying cycle, but colors varied at different points in their laying cycle. The more eggs the laid the lighter the egg color got. The hens that laid 6 eggs a week would have their eggs get lighter quicker than the hens that only laid 3 eggs a week (but at the 10th egg each hens would be about the same color). I had another line that was bread over 4 years that was created from stock from a half dozen different bloodlines. Egg color in that line were not consistent at all. The while the russet hue was the same on ever egg in the old pure line I would find 3-4 different hues in the mixed line. I also would have some that only laid a #4 and the beginning of their laying cycle and some that would lay #8 at the beginning of their laying cycle. Some would have color fade as they got further into their laying cycle like my old line would and others would see a small initial drop after the first week or two of laying, but then hold that color consistently at the rate of 6 eggs a week all they way to end the end of the laying season.
So..
Example #1: My Marans X While Leghorn hens hatched from a #6 Marans egg and the darkest egg color she ever laid was a #4.
Example #2: My first Marans hens never laid eggs darker than a #5. Her eggs would fade to a light as a #3 (I know less that a #4 means that she didn't meet the Marans standard of perfection. Don't tell anyone). From some of those #3 eggs I got hens that laid #6 eggs at the beginning of their laying cycle.
Example #3: From my mixed line I had a Hen that laid #8 eggs at the beginning of her laying cycle that was still laying #6 and occasionally a #7 egg all the way to the end of her laying cycle. None of her offspring ever laid #8 eggs at the beginning of their laying cycle. More significant though was that some laid even solid colored eggs while others laid eggs with dark brown freckles but with a lighter base color. Some laid a more brow hue of egg color and others laid a more red hue of eggs.
If you have nothing else to go on, then the egg color that they hatch from is what you had to use for your starting point, but that tells you less than half of what is going on with the breeding pair so a researcher would not accept that as a good measurement and hobby breeders that are serious about improving egg color at a minimum will know what range of egg color each hen in their breeding pens is laying over a full laying season multiple laying seasons and those that are doing more than that will know the range of egg color for the offspring or each cock and egg color contribution of every cock bird in their breeding pens is contributing too.
