The chickens at the farm we live on do receive organic feed during the winter, and the summer, but they usually just scratch it under the soil rather than eat it then.
In the spring, summer and autumn, the yolks are orange like fresh carrots from black soil (ranging from deep orange to deep yellow-orange from spring to autumn), and as the winter wears on, the yolks go from yellow-orange to deep yellow.
Our friend who lives on the other side of the country feeds his chickens and they do roam, but have not much to forage because of the terrain. Their yolks are still very rich, but vary from light yellow to deep yellow, depending on which hen laid them. Those yolks were still very strong, stood up in the pan and tasted delicious, and thick. There was only one hen who laid pale yellow yolks, but her eggs were very rich and the shells were very strong, whites were strong and properly divided and the yolks stood up too, so I think that's just the sort of egg she laid. I don't remember what breed she was, but not a common one. The shells were pale green.
My favourite is the bright, deep orange yolk though.
That only lasts for a few months here. I can't wait!!!
OP, I think it's fine as long as the chickens know they can go out and peck. Some organic farms do have a door for their chickens, but they are trained to think they can't use it, so it's of no use to them anyway, and they can still be classified as free-range, even though they don't go out.
I haven't heard of pastured chickens not wanting to be out and pecking; we've usually had a lot of 'fun' trying to get them to go back in at night because they really do prefer to be out all the time. The chickens here clamour at the barn door in the morning and trample one another to get out and then run away when they see someone coming to put them back at night.