 The intensity of black pigment on yellow Labradors is controlled by a separate gene independent of the fur colouring . Yellow Labradors usually have black noses , which may gradually turn pink with age ( called " snow nose " or " winter nose " ) . This is due to a reduction in the enzyme tyrosinase which indirectly controls the production of melanin , a dark colouring . <unk> is temperature dependent — hence light colouration can be seasonal , due to cold weather — and is less produced with increasing age two years old onwards . As a result , the nose colour of most yellow Labradors becomes a somewhat pink shade as they grow older . 
