North Carolina vs. Duke. Kansas vs. Villanova.

Blue vs. Blue vs. Blue vs. Blue.

There’s going to be a whole lot of one primary color this weekend at the men’s basketball Final Four in New Orleans. But don’t you dare say those blues are all the same. Each university has its own shade, a color it reveres and often fiercely protects.

For U.N.C., it’s Carolina Blue, a sky blue color. The other three are darker, but each distinct: K.U. Blue, Duke Navy Blue and Villanova Signature Blue.

North Carolina can trace its link with light blue to the 18th century, when a debating society chose it as its color, said Fred Kiger, a historian of the university. By the 1880s, the football team had adopted the color. At that time, the blue was far lighter than today’s color, but it gradually became richer, in part because that looked better on early color TV sets.

The designer Alexander Julian, who revamped the team’s uniforms in the early 1990s, has his own definition: “the color of the sky in Chapel Hill over the Old Well around noon.”

Defining shades of blue may feel like an imprecise concept, but in fact colors are specifically classified by the Pantone Matching System. The method is used by printers and designers to ensure consistency. It categorizes about 2,000 shades.

Carolina officially uses the color defined as Pantone 542. But Julian said he used the similar, but not quite identical, Pantone 278C for his uniforms. Each is far lighter than the blues of the other Final Four competitors, which have gone to “the dark side,” as Julian put it.

Kansas’ history with blue goes back to the 1870s, though there was a brief flirtation with crimson as its primary color in imitation of Harvard. Its current blue, Pantone 293, is joined in the university’s color scheme by crimson, Jayhawk Yellow and gray.

The Kansas Jayhawk mascot has been blue for more than 100 years. (Don’t go seeking this blue bird in ornithological tomes. “Jayhawk” was a slang term for antislavery guerrillas in the antebellum years.)

Duke’s still darker blue, Pantone 280, dates officially only to 1965, but its teams have been wearing the color since long before. The team’s nickname, Blue Devils, derives from a French fighting unit in World War I.

And Duke doesn’t fool around with the precision of its colors. Its branding webpage admonishes: “Any adjustment to the opacity or saturation of these colors is prohibited.”

Villanova’s blue, Pantone 281, is awfully close to Duke’s, but slightly darker. Nova uses light blue in its logo as well (for the record, that’s Pantone 298). The navy blue color was chosen in 1900 by the student body.

“Psychologically, people bond to the colors of their surroundings,” Julian said. “We as humans are bonded to sky blue in a way that is uplifting and enlightening. Dark skies mean trouble, and blue skies mean clear sailing.”