Krypton and a mix of other gases are most often used to make neon lights with a greenish-yellow glow. However, many signs contain neon gas or a mixture of neon and mercury vapor and simply use colored tubing or fluorescent coatings to produce the yellow-green effect.
Neon lights are also known as gas-discharge lamps, as they are designed to put inert gases under high pressure so that they conduct electricity. They work by utilizing a tube that has an electrode at each end. The tube is filled with krypton or other gases at low pressure, and a high voltage of around 1,000 to 5,000 volts is applied to the electrodes, producing light.