I'm blond with a dark haired husband. We have two blonds- one a very light almost white blond, the other a bit more honey blond. The third child has light brown hair with red highlights.
Hair color is determined by multiple genes, not just singular ones passed on from each parent. Therefore there can be many different variations of hair color, and it almost doesn't matter what color the parents hair is (my parents are both dark, and had three blonds, one brunette).
Eye color is a bit more singular gene specific. Blue eyes are recessive. For a child to have blue eyes, it would need to inherit a blue gene from each parent. A blue eyed parent can only pass on blue genes, while a brown eyed parent may have brown and/or blue eye genes, and could pass on either.