LET’S SAY you own the color black. You make a lot of money selling black stuff. Whenever anyone thinks about black, they think of your name. Your brand, your logo, your corporation are intrinsically linked to the color black.

But now you want to diversify. Now you want to sell something yellow.

What do you do?

If your name is Guinness, you make yellow . . . and then call it black anyway.

Or more specifically, Guinness Black Lager.

Make no mistake, the newest brew from the famous Irish stout brewer is, in fact, black as ink. But it is not a stout; it isn’t even an ale. It is as light-bodied and crisp as any other premium European lager.

When Guinness rolled out its new bottles last month, it conducted samplings in which it asked drinkers to taste it side by side with Belgium’s golden lager, Stella Artois.

No, you would never confuse the two, unless you’re in the habit of wearing a blindfold.

But that’s who Guinness is gunning for – the likes of Stella, Heineken, Grolsch, Carlsberg and Peroni.

Yes, the very company that has made billions selling black stout wants in on premium yellow lager because, these days, that’s where the big bucks are.

Now, you might rightly wonder: What about Harp Lager?

It’s also brewed by Guinness (its name is a tribute to the Guinness harp logo) and it’s actually yellow. The problem is, it’s not called Guinness. And, at least in America, Harp is a half-dead brand.

Then why not make a yellow lager and call it Guinness? Been there, done that, pal, and the result – Guinness Gold, circa 1980 – is best forgotten.

“We could have easily made a blond lager,” said Guinness master brewer Fergal Murray. “But we wanted to extend our brand . . . We wanted a stand-alone lager with the Guinness character.”

And Guinness’ character is nothing if it isn’t black. So that’s what they’ve come up with: a yellow beer that’s actually black.

This whole lame-brained scheme smells like something that the business nerds at Wharton came up with after a night of Jager shots at Smokey Joe’s. Eventually, though, someone in the brewhouse actually had to create this Frankenstein.

It wasn’t as hard as it sounds. Black lager is an old German style known as Schwarzbier. (The brewery is careful not to call it that because, well, speak English!)

This version is fairly typical for the style. The roasted malts are mainly added for color, not strength or body. Its aroma is quite mild, and its body is not nearly as luscious as Guinness’ stout. Its roasted taste arrives only in the finish, then quickly fades into the forgettable hereafter. It’s not as hearty as Germany’s Kostritzer Schwarzbier or even Samuel Adams Black Lager.

It’s a dark beer for yellow-beer drinkers.

But will they give up their Stella Artois? My first guess is no.

The Guinness brand is inherently hearty: black-and-blue soccer fans belching down full-bodied perfect pours in rough-around-the-edges “authentic” Irish pubs.

But it’s all about advertising, isn’t it?

And people who drink overpriced Euro-lagers are probably the easiest consumers to fool. They’re mainly impressed by (expensive) labels, and they don’t care what it tastes like as long as it’s inoffensive.

Which explains why Guinness advises, “The lager should be chilled and enjoyed responsibly straight from the bottle.”

That way, everyone can see the label and will be duly impressed by your fine taste.

And you, my friend, won’t even notice that the imported yellow lager you’re guzzling is actually black.

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