OP, have you actually shagged (m)any women?
Hair colour, hair length or lack of hair has nowt to do with libido and talent in the sack. Physical build or disability may be limiting but the deviant mind is mighty good at making almost anything work. Sexual health is also not a determinant of ability.
Plenty of blondes we've encountered have been shit, as with every other variety of SP.
Perhaps you should ask which SPs who changed their hair colour performed better (or worse) with which hair colour?