Why do you say they have red hair although I see they have actually orange-gold hair?
I don't think I should go see an ophthalmologist?

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Hi some describe it as auburn or titian.

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To generalize

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Because "Redhead" sounds much nicer than "Orangehead".

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"Red" is simpler to say! :P  It's not a specific sense, but a general, simplified meaning.  Much like how I'm called "white" even though my skin is a fleshy pink.

What do you say in Korea?