Is it Appropriate?

I love brown too. I see no reason why you shouldn't wear it. I'm sure it is probably more tasteful than the bridesmaid dresses if the weddings I've been to are any comparison. I think Brides want to be the queen of the ball and therefore make the bridesmaids look less wonderful than themselves. Besides there is many shades of brown. I say wear it and enjoy the wedding.

It is hard to say. If you accidentally wear the same colors of the bridesmaids dresses then that seems fine. But if you know the colors I wouldn't wear the same color. It looks really odd when someone is wearing a dress similar to the wedding party. Especially when you look back at the pictures

I've seen a guest wearing bright red gown when the bridesmaids were wearing burgundy gowns. I don't see any problem with that. You are only one of so many attendants, and plus you don't wear white as the bride wears. If she is your best friend then maybe you can ask her opinion if you feel so unsure about it, but then again if she is your best friend and happened to not choose you as bridesmaid she might not like the idea. Anyway, you can decide which way is best after all your brown dress might not be exactly the same brown for bridesmaid dresses.

I've never heard that it's inappropriate to wear the same color as the bridesmaids. You shouldn't wear white like the bride, but I think your brown dress should be alright. It's probably very different from the bridesmaid dresses anyway, and you could always use accesories that will further set your dress apart from theirs.