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—warmerâ