The bird's diet will affect the color and taste of the yolk. A deep orangey yolk means the hen is eating what chickens are supposed to eat. Seeds, grasses, greens, bugs, fruit, meat, etc. That's why home grown eggs taste better than commercial eggs. Those hens are fed only processed feed. The outside (shell) color will stay in the same shade all of a hen's life (unless there is a physical problem.) When the hen first starts laying, the eggs can be darker, or more intense, than they will be toward the end of the hen's cycle. They are more richly colored after a molt and in the spring, less so prior to molt and in the fall. Egg size will normally increase with age of the hen although small (wind) eggs are not uncommon in pullets and sometimes older hens. I got the smallest egg I've ever gotten last night, It is the size of a Peanut M&M! I assume its from one of my young pullets just starting her cycle. The color is like an airbrush, it sprays color on and the color is darker when it's full and fainter when it's getting empty. Shells are either white or blue, "spray paint" is varying shades of brown or reddish-brown. A white shell with brown paint will be brown, a blue shell with red-brown paint will be green. If you pay close attention the color and shape of your eggs, you may be able to determine the hen that laid it by theses characteristics alone. My egg customers laugh when they point out a pretty egg and I say, "Henrietta laid that one!"
