The most interesting thing about this thread are the fair numbers of people who justify that they are redheads or who seem uncertain. If you are a redhead, you...are...a...redhead.
You don't need to say...it looks brighter in the sun.
You don't need to say...I dye it.
You should never say...I guess so.
You are or are not a redhead. If you "Guess you are" or "Sort-of are" then you probably are not.
I burst into flame in direct sunlight. I am a redhead.