Fair is the opposite of dark. So, any person whose hair is lighter than light brown might be called 'fair' (NB in the past 'fair' was also a synonym for pretty/beautiful - you'll still come across this in old songs etc). https://www.dreamstime.com/stock-images-portrait-smiling-girl-long-fair-hair-natural-make-up-image30195154 Blonde is is closer to light gold or white. https://www.dreamstime.com/stock-photo-beautiful-young-blonde-girl-pretty-face-beautiful-smiling-eyes-portrait-woman-long-hair-amazing-looks-image98386316

Fair hair is a rather old-fashioned term. It was used to describe what we call blond/blonde today.

synonyms))

fair hair are cheaper