Just as the worlds of architecture and industrial design have played with novel color combinations in recent years, so has the luxury watch sector, with brands including ArtyA, Chronoswiss, Oris and Zenith capitalizing on color as a way to stand out in the crowded Swiss watch field.

By using cutting-edge techniques and processes such as lasers and chemical alterations of materials, their watch parts not only display distinctive hues, but some change dramatically depending on light conditions and viewing angles.

One of the most technically advanced techniques is atomic layer deposition (A.L.D.), which, at a company called Positive Coating, is carried out at a nondescript industrial building in La Chaux-de-Fonds.

On a recent work day, a group of seven women in white lab coats and hairnets prepared to put more than 100 watch dials and parts into several metal chambers, each about the size of a home freezer measuring about half a cubic meter (17.6 cubic feet). Once the pieces were inside and the chambers turned on, their powerful pumps created vacuum pressure and tinted the pieces through a molecular process.

In an extremely simplified explanation, A.L.D. involves layering a series of thin films on a surface — and the color perceived by the viewer is determined by the number of layers. “A.L.D. is always transparent; it contains no pigment or paint,” said Lucien Steinmann, co-chief executive of Positive Coating, which was founded in 2004 and specializes in surface treatments using A.L.D. and P.V.D. (physical vapor deposition) technology. “Depending on its thickness, this coating is experienced by the human eye as different colors.”

Layers of A.L.D. film are created when, Mr. Steinmann said, “in the chambers we introduce a gas of molecules that could come from silicon, aluminum, tantalum or titanium.” The choice of material determines the shade of the color, so the company and the client usually decide together to select which material to use.

The thinnest coating is 10 nanometers (0.394 millionths of an inch), which takes about an hour to achieve and would be some variation of brown. Another 300 nanometers of coating, which would take more than 24 hours to accumulate, appears to be green — the color that takes the longest time to achieve. Most colors of the spectrum can be achieved within about 24 hours.

The A.L.D. process was invented in 1974, and has been used by the semiconductor industry to prepare microchips since the 1990s. Positive Coating introduced an adapted version of the technique to the watch world in 2014 when it began offering what it called “decorative A.L.D.” Since then, other competitors have emerged.

“Since 2020 we have been working with changing colors,” Mr. Steinmann said, and that was the beginning of such color treatments for watches. Use of the technique, however, is limited to watch dials and internal parts as A.L.D.-treated surfaces scratch easily.

If you twist and turn Chronoswiss’s Open Gear ReSec Paraiba watch, the color of its A.L.D.-coated dial changes from sky blue to light green, then to a military-style olive green and a dark jungle green, and finally from a petroleum blue-green to pale purple.

The colors are similar to those seen in the tourmaline gemstones found in the Brazilian state of Paraíba — a color coincidence that prompted Chronoswiss to name the model for the region. “You can see around 20 different colors in this watch dial in the sunlight,” said Oliver Ebstein, Chronoswiss’s chief executive.

Mr. Ebstein said Chronoswiss often uses green in its watches, “and we met Positive Coating when we were researching new greens that would not block the effect of our handmade guilloché.” He was referring to the engraving that its artisans do on many of its dials, using the company’s century-old rose lathe.

It turns out, Mr. Ebstein said, that guilloché actually enhances the effects of A.L.D.: “The light will refract differently on the top of the surface than on the lowest part” of the engraving, he said, and the color “will change with the angle of the light.”

What exactly is color?

“Color is exactly what it seems,” said Susan Farnand, an associate professor in the Color Science Program at Rochester Institute of Technology in upstate New York. “It is a perception and nothing more.

“What we are seeing is not part of the object — it is our perception of light interacting with the object.”

Dr. Farnand said color-change watches reminded her of similar shifts that occur in nature, such as on insects’ wings and birds’ feathers. “In nature, structural color changes happen because of very thin layers with varying structures,” she said. “This is on a nano scale where these natural structures differentially scatter light based on wavelength.”

Color change also can come from within the watch’s parts. Sapphire crystal cases that change color, for example, were used in the NanoSaphir collection from ArtyA, a watch brand with headquarters in the Swiss village of Meinier, northeast of Geneva.

“We are inspired by nature,” said Yvan Arpa, who founded the brand 14 years ago. “For instance, by the naturally color-changing gemstone alexandrite.”

Mr. Arpa and his older son, Stanislas, demonstrated the effect with a half dozen watches taken from the safe deposit boxes lining the vault of a former bank building that the brand uses as its headquarters.

Stanislas Arpa, 26 — who joined the company early last year and has a bachelor’s degree in microtechnology from HEPIA, the University of Landscape, Engineering and Architecture in Geneva — shielded the watches from the fluorescent ceiling lights so they were illuminated only by a lamp with a special bulb that mimics daylight.

Each one instantly changed its appearance: smoky amber to jungle green; tiger’s-eye brown to Barbie pink; Nordic ocean blue to algae green; cloudy gray to cherry blossom pink; and sky blue to deep purple. “The change happens when the light temperature is 6,000 degrees Kelvin or above, which is comparable with daylight,” he said.

ArtyA declined to identify the company that makes its cases, but Stanislas Arpa said that it had manipulated the chemical structure of the sapphire crystal: “This is why it emits lights on different wavelengths — different colors — under different light conditions.”

“It seems like a magic effect,” Yvan Arpa said. “But it is very rational, it is mathematical in the end.

“And this opens new doors to watchmaking. I think a new generation doesn’t want to buy the same watch as their grandfather.”

Manipulating lighting is one of the key jobs at Fisher Marantz Stone, the company whose credits include designing the lighting for Tribute in Light, the now-annual memorial for those lost in the attack on the World Trade Center towers on 9/11. And when its president, Charles G. Stone II, saw images of the ArtyA watches, he said they were “a lot of fun.

“They tell you if you are inside or outside,” he said. “To have a watch respond to the environment is very playful.”

The Oris ProPilot X Calibre 400 Laser is a watch with a titanium dial and case. The dial, when viewed perpendicularly, is the basic gray of titanium. But tilt it just a bit, and the vertically brushed dial turns a shimmery purple, blue and green.

“The dial has no pigment; it has been treated with two laser processes,” said Richard Siegrist, Oris’s product development engineer.

First, however, the dial is sandblasted, creating a visible vertical brushed pattern. Those minuscule peaks and valleys actually enhance the effects of the laser processes (done at a laboratory affiliated to the Eidgenössische Technische Hochschule, a public research university in Zurich).

The initial lasered pattern is 400 to 600 millionths of a millimeter in depth, and when normal light hits it, the red wavelengths are absorbed.

“This is referred to as interference — interfering with the ability to reflect,” Mr. Siegrist said. “The shimmering rainbow effect is caused by a second laser treatment, which creates a surface that splits the light.” (The rainbow on the dial is dominated by greens, blues and purples because the reds have been absorbed.)

Rolf Studer, Oris’s co-chief executive, said he doubted the brand would ever return to creating just monochrome dials.

“We have become less normative in many aspects of our lives, that’s why people dare or want to express who they are and how they feel,” he said. “Color is an expression of emotion and personality. Color is everything.”

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