Lights are measured in temperature—which has nothing to do with how hot the bulb is, but rather whether there’s a warm or a cool cast to the light. The higher the number, the cooler the color.

Different jewelry is flattered by different temperatures. Under the wrong light, pieces can look dull and unimpressive, but a piece under a light that flatters its dominant hue will be an eye-catcher. Econo-Lite’s Howard Gurock suggests these matches to give your gems the best effect:

Yellow gold and gemstones in warmer hues  (i.e., reds and yellows) look best under a lower-temperature—warmer—light, generally in the 3,000K to 3,500K range. Silver and gemstones in the middle of the color spectrum­­—and pieces with multiple colored stones—respond best to light in a medium temperature range of around 4,000K. Pearls, whether white, gray, or brown, fall into this territory as well. For diamonds and platinum, stay cool. Some experts say diamonds look best under temps as high as 6,500K, but Gurock prefers lights between 4,000K and 5,000K. The closer you go to the higher end, he adds, the more important it is to have a high-quality bulb, since cheaper ones in the 5,000K range can emit an unappealing bluish tint.

And though diamonds look best under a cooler-temperature light, there’s a caveat, says GRID/3’s Keith Kovar: “When you have those very cold temps of 5,500K and above, people’s skin starts to look washed out. It can look stark.”

Mike Clow’s Light Source Specialties has developed a product targeting the need to balance hues that show off diamonds and those that create an inviting retail space: “Jewelers have been mixing the lights for years,” says Clow. “We’re using multiple color temperatures to light a showcase [within the same fixture].”