For generations the view has held strong that while girls must dress in pink to be girls, boys can't do anything with pink, lest they turn into girls.
It's the view that's determined the color scheme in many a kids' bedroom, clothes and toy closets, and that has held strong through decades of change.
But, in today's 21st century world, is that view changing?
Take Gregory Jobson-Larkin's 6-year-old son, James, for instance.
"James' wardrobe choices are pink, purple and chartreuse," Jobson-Larkin, of New York City, told "Good Morning America" of the colors his son reaches for. "And he does have a pink pair of cowboy boots."
And Jobson-Larkin is okay with it.
"Got no problem with the pink shirt," he said.
James' choices may not have gone over so smoothly when his own father was a boy, but today the fashion-forward, seemingly color blind 6-year-old may just be on to something.
Recent episodes of TLC's popular reality show "Toddlers & Tiaras" have featured "pageant boys" competing right alongside girls in pink and sequins, and "pageant dads" standing right next to the "stage moms" coaching their little ones to the crown.
A near media maelstrom erupted in April when a photo of clothing company J. Crew's president and creative director Jenna Lyons painting the toenails of her son Beckett pink ran in an ad sent to customers.
Add in the books and blogs in support of boys and their pink choices and you see that young James is exactly right. Pink is in.
"It's a big deal to see boys dressed in pink because, simply, it's not the cultural convention," gender expert, and author of the book "Pink Brain, Blue Brain," Dr. Lise Eliot, told "GMA." "But it's nothing hard-wired. Boys are not innately aversive to pink and girls and are not innately attracted to pink."
Boys may not be 'innately averse' to pink but what about their fathers, the generation of men who grew up in a not-so-open society, one in which blue was, without question, for boys. Is pink also "in" among these dads, fathers like Jobson-Larkin whose young son already clearly prefers pink?
ABC News gathered a panel of four fathers of sons, Jobson-Larkin included, to see where the men raising this new generation of gender-neutral kids fell in the gender color war.
The dad's sons, we learned, had varying interests and preferences.
"My son is into trucks and yellow is his favorite color," one dad said.
"My son loves golf," said another.
"My son likes Tae Kwon Do," said a third. "He also loves everything pink and purple.
For the dads who saw their sons bending the gender color lines, what was their true, gut reaction that first time their little one chose pink over blue?
"I verbally said, 'Is that the color you really want? Look at…there's some other colors,'" Jobson-Larkin recalled. "I really didn't know to handle it when it first happened."
"I really wanted him to choose a different color," he told the panel. "It was really a reflection of me to be honest, of my own struggle."
And what if, in a perfect world, the dads could choose whether their son grabs a pink shirt or a blue one?
"Pink shirt," one father replied immediately. "I'd want him to go to the one he was drawn to."
Even the fathers who firmly wanted their sons dressed in blue acknowledged that, in the end, it should be their son's decision to make.
"I'd prefer my child to choose blue," said one dad. "But if he wants to choose the pink shirt over the blue shirt, it's up to him."
"I follow my child's lead," another agreed. "So it's not really the point of what I like. It's the point of what my child likes."
Dr. Eliot says fathers like those on the ABC News panel opening up to non-gender based color choices is having an impact on this generation of children.
"We actually created the color scheme that we now define as gender based," Eliot told "GMA." Kids learn that one color is "bad" for them from adults."
Examples of the gender colors breaking down are even showing up where the stereotype has long held most firm, the consumer marketplace.
Young Boys Weigh In
A bubblegum pink scooter put on the market three months ago in the U.S. was heavily marketed to both boys and girls after its maker, Micro Mini Scooter, conducted an in-house survey that showed 88 percent of parents surveyed were okay with their sons playing with it, pink and all.
While the majority of those parents surveyed were okay with a pink toy for their son, ABC News discovered that, when it came to pink clothing, the fathers on our panel did have a limit.
"Pink tutu? Problem," Jobson-Larkin, father of pink-wearing, six-year-old James, said when we held up the frilly, definitely pink, piece of attire.
"My son did wear a skirt sometimes to preschool, and we allowed that," another father chimed in.
"I struggled with my own comfort level with that," he said. "What I was really concerned about was that he'd get teased and not be accepted."
So ABC News went straight to the source, assembling a group of five 6-8 year old boys, to see if they too worried about acceptance and teasing among their peers not-in-pink.
"I don't really believe in the 'girl colors boy colors' thing," said one boy in our assembled group.
"I like pink. I also think the 'boy color girl colors' is not fair," another agreed.
When we asked the boys to pick a shirt and try it on, two boys chose pink, and even made a point to bond over it, giving each other fist pumps in the air over their selection.
"I would never be worried about wearing pink to school," one said.
Despite their enthusiasm for pink, however, the boys showed that, just like their dads, there is still a limit in today's culture of how far "boys in pink" can go.
"I just wouldn't want to cross the line with a princess on the shirt," one boy said when we asked about wearing a pink shirt featuring a princess on it to school.
"They would probably laugh at me and I would kind of be a little humiliated if that happened," he said of his classmates' reaction. "I just wouldn't want to go there with it."