There used to be a term for older women – Blue Hairs – named for the steely rinse used to enhance their graying locks. Not always intended, the color could have resulted from a bad dye job or bad perm. But “blue hair” was not at all a respectful or flattering term.

Still, I’m sure those blue-haired women were making what they hoped was a subtle attempt to forestall the appearance of aging which they feared, and society validated, would make them feel invisible.

Thank goodness, subtle is out. And visibility is in. Now we have groups of women in their 50s and beyond who are stating their presence in living color. If some people think they’re too gaudy, well, fiddle-dee-dee, get over it. Like them or not, they’re not at home fading into the wallpaper.

The latest to go public are members of the Blue Thong Society. You might consider them an alternative to the Red Hat Society, that group of older women formed 11 years ago to display their vintage in ever-growing swarms of purple boas and red chapeaus.

But not everyone is the Red Hat type. Women do not deal with their experiences, even shared ones like milestone birthdays, in the same way. Yet, there’s strength in numbers, especially when you’re out to bust stereotypes having to do with age. And so a group of friends in San Diego decided to do it their way.

The Blue Thong Society was conceived four years ago when Mary Jo Wallo, an investment counselor and surfer in San Diego, celebrated her 50th birthday and two surfer friends gave her red hats. As a joke. Mary Jo knew about the Red Hats and appreciated their chutzpah but considered herself a bit hipper than the Red Hat image.

She couldn’t do the costume, she says. She and her friends remain true to their bell bottoms. And while she says, “We accept the fact that we’re all getting older,” she explains, “We’re young-minded. We’re hot and we surf.”

Mary Jo’s friends agreed she was more apt to wear a red thong than a red hat and that was the beginning of what is now a national group. In the development process the thong became blue, maybe because everyone in the charter group lived next to the Pacific.

Now Thongers have recruited women across the country who sport the Blue Thong logo, a frisky design that, depending on how you look at it, can resemble a flip flop shoe on a bare foot or a string undergarment on a round bottom. Members are not required to wear either variety of thong but happily wear T-shirts that say, “Fight Frump.”

Red Hats founder Sue Ellen Cooper, also from Southern California in Orange County, stated from the beginning that she hoped her Red Hat women would gather just to have fun, without an agenda. Mary Jo Wallo asks each Blue Thong chapter to work with a non-profit in their community. Her own, in Encinitas, sponsors a women’s shelter.

Thongers like to have fun, too, which I discovered when I spoke to a group in San Diego where the theme drink was a blue martini and they were still raving about last month’s sex workshop.

Founder Mary Jo, who combines a tight tanned surfer body with a business woman’s marketing brain, doesn’t feel competitive with the Red Hats. She told Sue Ellen, the Red Hat organizer, there are your Coke drinkers and your Pepsi drinkers. Your Adidas people and your Nike people. There’s room for us for all.

That’s right. We grow proud and old and this time if we color our hair blue we’ll make sure it glows in the dark.