Mammals have hair coloured by two compounds, the dark brown melanin and orange carotene, also found in skin and carotene in vegetables. Some has no carotene, but where both are present after a certain amount of melanin the red colour is covered up and not visible outside a lab test.

Human hair colour

Not all mammals however have the same colour hair. One of the most familiar, cats, also come in blue/grey. This is a colour found in some other mammals but not in humans. Cats however appear to have missed the yellow version although this is simply a low concentration of the usual two elements making the hair various shades of yellow.

It seems cats have a slightly different range of colour elements, and if anyone has more details specifically on grey and lack of yellow I'd like to know the substance creating it. Cat hair colours

Finally human grey hair/colour loss is a total loss of the colouring, the transparent outer keratin shell being transparent so appearing white.

So, I'm not getting elderly, I'm just experiencing the sudden transparent outer keratin shell being transparent so appearing white. Funny, they don't feel naked!

Which begs the question, "Why does it take so long for our hair to don its birthday suit?"

I can answer that. White (grey hair is the mix between white and original) hair comes from an auto immune reaction on the melanin in the hair which is mainly genetic. Once it kicks in the body starts destroying the melanin in the hair, although I don't know if there's an evolutionary reason.

Cold country animals however regularly shed their hair and evolved white snow winter coats which are not found in humans.

So does that explain why so many politicians whiten their hair? Are they really covering up a genetic failing? And how deep does that hollowness go in them? Does it pass their follicles and go into the brain?

Looking through the Ask archives I discovered a green cat due to an abnormality in its copper metabolism. Green cat

On St Patricl's Day we now have another thing to raise glasses to: Green cats. March 17th is just 2 weeks away.

Thank goodness the food given to a cat doesn't influence thier colour. Otherwise I would most likely end up with two pink cats - they adore salmon and tuna.

Amazingly this information just came up on the monster quiz. I always thought red colouring was carotene and brown/black melanin, but they are both different types of melanin. Being in the Monster Quiz I couldn't link the quiz directly but will find it and edit it in.

"Eumelanin is the pigment which gives black or dark brown hair its colour. Pheomelanin is the one which makes hair red. Caucasian people with red hair also tend to have light coloured eyes (blue, green and grey) and fair skin."

Hair colour

Tell that to my red headed brown eyed daughter and cousin.

I know they share all varieties but brown is the rarest. I know a few myself. But I can't think of many without fair skin.

If anyone can discover a cat with yellow hair or how they can have grey (not white) hair please let me know!

Why would anyone want to breed greenness into a cat? That's perverse!

I've never met a brown-eyed redhead, though my red-haired sister does have hazel eyes. Also, my godmother is a brown-eyed blonde, which is a great combo though I should think rather rare.

I think it is really weird when people "color" for their cat. Why do we have to do it? The original color is its own characteristics.

My hair is yellow but my parents have brown color hairs, I guess I got it from my grand-father

I thought a grey cat is dilute black.

Somewhere I have a book on cat genetics because I was curious on how my pure white cat gave birth to one jet black, two white and one cream (dilute red) kittens.

I'll check, but the grey cats I know appear to have solid fur with no mixture of light and dark. And I've yet to find a single example of a part or all yellow cat although humans and horses at least have the colour regularly. Maybe Dr Karl will know, I'll send him a tweet.

Dilute doesn't mean that it has some light and dark, it is something in the genes. White cats are not actually white, they are some other colour which is masked if I remember correctly. My little white female was from a black mother. I let her have the one litter so was amazed at the three completely different colours of cat, hence buying the book.

I'm reminded of the last paragraphs of Iris Murdoch's first (and in my opinion most readable) novel "Under The Net". The woman who keeps the narrator's local shop has a tabby she-cat and she's always trying unsuccessfully to get her to mate with a local Siamese. When the narrator returns after an absence, the cats have mated and the shopkeeper has a litter of kittens:

"What puzzles me," said Mrs Tinckham,"is why those two should be pure Siamese and the other ones quite different, instead of their all being half tabby and half Siamese".

"Oh, but that's how it always is. It's quite simple," I said.

"Why is it, then?" said Mrs Tinckham ... I stopped ... I laughed and Mrs Tinckham laughed.

"I don't know why it is," I said. "It's just one of the wonders of the world."

I read a little about it, cat fur genes can be masked for all features so a litter can have examples of any variety in the litter if either parent carries them with or without showing it in their own fur. Also although no domestic cats I've seen have had any yellow in them of course tigers and leopards do, so presumably depends where they bred from originally.

The grey hair seems to be the only mystery now as hair colour is supposed to be melanin (black to yellow depending on the percentage) and carotene (orange, hidden by melanin), with white having none at all and just actually transparent shafts refracting the light to appear white. Grey cats have solid grey hair, so all I need to discover now is what pigments are in it. They also have multicolour hairs which can be black at the skin, beige in the middle and black at the tip which is standard for tabbies like mine.

I thought a grey cat was a dilute black.

I had a white female, daughter of a black female. She had three white kittens, mine being one of them. My white cat had a litter, two white, one solid jet black and one cream (dilute ginger). White in cats isn't a colour, it is a mask so presumably my white cat was really a black cat. Therefore dad was probably a ginger or cream.

I'm puzzled why some people think brown eyes with red hair is rare. I've known numerous people with that coloration, including my father, daughter, and niece.

I'll post a photo of my neighbour's grey cat tomorrow in photo a day. I will also ask Dr Karl as he specialises in scientific mysteries. I've seen red hair with all colours of eyes although green was the commonest.