There are 2 colors of egg shells, white and blue. Brown eggs are one of those two colored eggshells with brown pigment laid on the outside layer.
Brown eggs are white eggshells with brown pigment layed on top. Green eggs are blue eggshells with variable amount of brown pigment laid on top- the amount of brown pigment can vary from just a small amount, leading to light green eggs, to a heavier coating, which causes olive eggs.
Although a very light coating of the brown pigment may make an egg look pink---it is really a very light beige. Some eggs look cream, one poster on the BYC forum had an avatar with an egg that had such light brown pigment, it looked like a pearl.
Another variation for you to think about is the chickens that will lay spotted eggs. I think some Welsumers lay a brown egg with darker brown spots. Those are some interesting and pretty eggs. There is even a grocery near here that has brown eggs, with dark brown spots. For a couple of eggs my BPRs were laying light brown with spots (darker brown, some lavendar and some blue spots)....but they subsequently settled to solid colors.
We started getting spotted eggs last week and have suspected they are probably from our Welsumer, but wondered if the other possibility was our Maran. We've only been getting eggs for 2 weeks total and 3 of our 7 are laying. The others are plain brown eggs from our BR and our BO. I was out of town last week and my husband didn't pay much attention to who was in the box. They are so pretty!