Over the years I've noticed how the color, size and shape of eggs vary. Some are almost round while others are narrow with pointed ends. Some seem to have shells laid in sections, others are smooth. It may vary from bird to bird, sometimes day to day. Some colors and their intensity are breed related while some variations exist within a single breed. Of course too, you can get tiny "fart" eggs and huge double yolkers. In all, it keeps life interesting.
What's inside that egg?
If it has a decent yolk, do you have nay birds that are close to onset of lay?
Fairy, fart, wind, rooster eggs are usually from a tiny piece of tissue breaking loose from the reproductive tract, or an immature ova(yolk) and the body forms an egg around it. Color can be darker than 'normal' as the pigment coating released has to cover a much smaller area so is thicker. Can happen with any age layer, but more common with new or older layers.
I think it's explained in this excellent video, which is worth watching regardless: