There’s nothing rare about Starbucks’ Unicorn Frappuccino — in fact, the...

A Brooklyn cafe owner says that when she came up with the recipe for a colorful “Unicorn Latte,” she thought it would be a nice way to peddle the new so-called superfood blue-green algae.

Little did she know that Starbucks would rip off her idea and change it with sugary syrups and artificial dyes, prompting singer Katy Perry to famously spit it out and forever give her own concoction a bad name, she says.

“I felt a lot of excitement and pride that something good for you could be as fun and colorful as junk food,” Madeline Murphy, co-owner of Williamsburg’s The End cafe, told The Post of her drink.

“No one ever wanted it to by synonymous with spitting something out.”

Murphy is now suing Starbucks in a $10 million trademark infringement action.

She said the magic ingredient in her own drink is a potent, allergy- and cholesterol-busting powder made from the algae.

Unlike Starbucks’ version — the Unicorn Frappuccino, which sold out during its limited release last month — Murphy said there’s nothing artificial about her concoction.

She said she’d been toying with the idea of mixing blue-green algae in a “tasty drink” for three years.

Late last year, Murphy, 32, finally cobbled together a recipe that blends the bitterness of lemon juice with the natural sweetness of vanilla bean and Medjool dates.

The psychedelic hue is in part thanks to the algae which is harvested from a lake in Oregon.

“The ingredients are so potent and powerful that I started to describe them as magical,” Murphy said about her decision to name the concoction after the mystical unicorn.

She saw a rush of positive press when she launched the product in December. The New York Times dubbed the $9 drink a “healing Unicorn Latte” while TimeOut called it a “really fancy warm juice cocktail.”

“The End’s Unicorn Latte became viral and was all over the internet. A simple Google search reveals it,” said Murphy’s lawyer. Josh Schiller, with the law firm Boies Schiller Flexner LLP.

But Starbucks insists that it was just putting its own twist on what was already a trend.

A spokesman for the coffee chain pointed to a “unicorn hot chocolate” that an Anaheim, Calif., sweet shop was selling the same month that Murphy started marketing her latte.

“The Starbucks Unicorn Frappuccino blended beverage was inspired by the fun, spirited and colorful unicorn-themed drinks that have been trending in social media,” the company’s spokesman told The Post.

He called Murphy’s claims “without merit.”