Pink is for girls; blue is for boys.
That's a fact. Isn't it? The evidence is all around us.
Go into any toy shop or clothes stores aimed at youngsters and you'll find shelf upon fluorescent shelf glowing bright pink for the female of the species, and for the males, much more toned down, rack after rack of every shade of blue.
It's a marketing conceit that all things fluffy and soft must be for girls; and all things tough and dangerous are for boys.
And it's a marketing lie.
Just before Christmas, one store – Hamleys - finally cottoned on to the fact that we parents are fed up with this stereotyping and stripped its stores of gender colouring. The store has removed the pink and blue signs which pointed customers in the direction of toys for boys and toys for girls.
Instead, the shop now organises toys by category, with red and white signs guiding children and parents around the store.
And as much as it's a step in the right direction, Hamleys is a rather posh store where mainly the well-off shop. The rest of them, though, are still firmly entrenched in their gender stereotypes and unless they believe there is profit in a change of policy, it's likely to remain that way.
How different it was in the early 1900s, when blue was for girls and pink for boys.
DressMaker magazine agreed. "The preferred colour to dress young boys in is pink. Blue is reserved for girls as it is considered paler, and the more dainty of the two colours, and pink is thought to be stronger (akin to red)."
What prompted the switch is unclear, but it had been made by the time Adolf Hitler ordered the classification of homosexuals. Those deemed "curable" were sent to concentration camps and labelled with a pink triangle. This suggests that by then, pink was associated with femininity.
In my experience, as a stepfather to a 10 year-old girl and dad to boys, aged seven and four, kids are kids – yes, I know, and bears do their business in the woods – but what I mean by that is they are all individuals: some are born soft and fluffy; others tough and competitive.
It's only commercial brainwashing that steers them in one pink direction, or blue.
I never really understood the differences between boys and girls until I became a stepdad to my wife's daughter eight years ago. But those differences were nothing like I had imagined.
And then Daisy came into my life. She's 10 now, so I have known her since she was a year old. And she is nothing – nothing – like the little frilly girls I imagined in my youth.
In fact, she is more of a 'boy' than I have ever been. And more of a 'boy' than her brothers. She is strong and confident, determined, tenacious and fiercely competitive. She is gregarious and popular, filling rooms with her effervescence wherever she goes. She is the opposite of a shrinking violent – more of a Bloomin' Ada!
She is as delicate as a flowering cactus, and occasionally just as spiky. As robust as wrestler, but without the amateur dramatics. She is an Act-First-Attend-Casualty Later kinda gal. She never thinks about the consequences, never assesses the risks of her often foolhardiness. Feet first. Take the plunge. Splat! On to the next one.
Her seven-year-old brother, Tom, is the opposite, as gentle as his sister is fierce; softer than an eiderdown with a marshmallow stuffed in it. He loves to cook, he loves to clean.
He gets himself up in the mornings, then prepares breakfast for his sister and brother, then helps me unload and re-load the dishwasher – all of this to the strains of my nagging voice urging his sister to get out of bed, get ready for school, and "For God's sake BRUSH YOUR HAIR – YOU'RE NOT A SCARECROW!"
Yes, there are differences between boys and girls, but they're not the ones that society dictates them to be.
Yet...here's the rub: Daisy loves pink; Tom loves blue. Why?
Perhaps it's because that's all there is to buy. The choice in stores is so limited to these falsely created social stereotypes of what girls and boys should be wearing, with no acknowledgment of the fact that each and every one of them is different.
Try to buy clothes for a little girl in any colour but pink and you might as well try looking for the Holy Grail. This is not because girls naturally prefer pink - it is because the people who sell us stuff want it this way.
So successful have they been in creating a girl's world painted purely in pink, that some children when shown the colour and asked to identify it simply say: "Barbie".
Is it healthy? I don't think so.
Sue Palmer, the author of a book called Toxic Childhood about how the modern world damages kids, says that the total obsession with pink stunts girls' personalities.
"I am very worried about it," she said. "We are creating little fluffy pink princesses, an image of girliness...which some girls don't want to go along with, but due to overwhelming peer pressure, are having to conform to."
It's clear from talking to other mums and dads and reading comments on online forums that parents feel we're fighting a losing battle.
"I try desperately to avoid pink clothes for my 21-month-old daughter," one told me. "But it's difficult to buy girls clothes in any other colour. I cringe when I walk through the 'girls' section of toy shops because it turns completely pink. When I buy her toys I try to go for gender neutral ones. When I play with her it's with footballs or on my skateboard. But she loves pushing around a toy pram. A friend bought her a Barbie doll (to my horror), and she loved it."
"Kids change, thankfully," said another. "My daughter used to love the colour, had to have her room painted in a particularly nauseating hue, but now can't stand it. Her change kind of happened about the time she realised she didn't like Barbie any more."
And another added: "I've always hated pink, it feels for me to have suggestions of fluffy, silly, girliness which doesn't suit my personality. My three-year-old daughter is very similar - her favourite colour is blue and she loves Thomas the Tank Engine, but I have no choice but to dress her in pink clothes, particularly on a restricted budget. Colour is an important expression of personality, and this is being restricted for girls."
But one argued that girls prefer pink because of nature, not nurture.
"When starlings are ready to find a mate, the base of their bill changes colour - males have a blue tinge and females have a pink tinge," she said. "Perhaps it's a natural choice?"
Yes, said this dad: "Our eldest daughter, five, is all about pink, and has been for years. This is despite our conscious efforts to not force pinkness on her."
Perhaps the tide is turning. Last year, an amateur rugby team in West Yorkshire turned out in a blue kit decorated with pink flowers.
And if more stores follow the Hamleys example, then perhaps pink for girls and blue for boys will one day become a thing of the past.