Can my chicken's egg color change?

First off, let me introduce myself. I am new on here, but have used the site for info. I am fairly new to chickens. I raised four Ameracuana ladies (spelling?) from chicks a year ago. We lost two in November and I replaced the with a Plymouth Barred and an Astralorp. In the fall-early spring my ladies are free range and can walk about our half acre yard. In a few weeks they will mostly be relished to their pen. We have a pool and chicken poo and pools don't mix! Plus I have a million kids running around all summer and it is better for all if they are cooped up a bit more for everyone's protection.
Anyway, I am only getting one blue egg a day. This means that one of my Ameracuana ladies is not laying. They had barely started laying before the winter when we lost the two (raccoons) and they went into shock and stopped laying for most of the winter. However, I am getting two or THREE brown eggs a day. On days I get three eggs I am happy, but about three times a week I am getting four eggs. I am trying to figure out how this works. The Ameraucana can't lay a brown egg can she? Today my son brought in four eggs. They had to lay them all between 8:30-2:30 because I checked when I let them out. One of the eggs is a lot lighter brown (almost a cream), but is certainly not the blue/green of an Ameraucana. I am puzzled. I thought they could only lay one egg a day! Ideas? Thoughts?

Did you get them from a hatchery or feed store? If so, your "Ameraucanas" are Easter Eggers, and can lay any color eggs...blue, green, pink, or brown...

I agree. It sounds like you have EEs, not true Ameraucanas. The Barred Rock and Australorp lay brown eggs, for sure. The EEs can lay pretty much any color, so it's very possible that one is laying a brown/cream egg. You only get one green egg per day, right?

Hens only lay one color in their lifetime. The shading may vary, and they may lay some with speckles, but the base color is the same. A hen that lays green eggs will always lay green eggs.

I did get them at a country feed store. When I had all Ameracuanas we never knew who was laying what so it could be that this lady never laid at all until this spring. One of my murdered ladies often laid in hidden nests so we were always guessing as to who did what. I bet she is the one laying the lighter brownish cream eggs. This solves the mystery! I thought they couldn't change egg colors, but weird things happen.