Pepsi cruises by in April.As devoted viewers of QI will no doubt recall, if you put a Siamese cat in a refrigerator it goes black. That is because the hair is temperature sensitive. The fur on the face, tail and feet ie the extremities, are always cooler, so always dark. However the body fur is warmer and stays pale.
Pepsi just released from a fortnight in the fridge*.It's to do with an enzyme in the hair called tyrosine. The enzyme is involved in the production of melanin, a brown pigment, but it is heat sensitive, breaking down if the temperature goes up too much.
*Or possibly photographed visiting in the January cold.