I saw a story on this once. In the UK, there really is a bias against red-heads (gingers)....to the point that peope dye their hair to avoid being detected. They are unexplainably thought to have lower intelligence, and just generally are looked down upon. For some reason, it fascinated me...but making fun of red heads has a little more bite in UK than it does here.
There is a Sherlock Holmes story, The Red-Headed League, that centers around a man with fiery red hair. I guess it could be said that he was depicted as having lower intelligence since he was hired to copy the Encyclopedia Britannica and didn't ask any questions until his job disappeared.
In the British kids TV show, Fireman Sam, one of the main characters is a fatherless boy with "ginger hair", who is portrayed in a lovable way, but is generally naughty and mischievous and sometimes the cause of the incidents that the protagonist has to deal with.
Dare I say it, to the British redheads are so bad they are practically Irish, which is to say they are almost subhuman in the British mind. Yes, there is still that sort of bias there. Muzzies are okay though.