Holiday lighting technology has been subject to considerable development and variation since the replacement of candles by electric lights. While originally used during the Christmas holidays as Christmas lights, modern electric light arrays have become popular around the world in many cultures and are used both during religious festivals and for other purposes unconnected to any festivities. Incandescent lights Incandescent light bulbs have been commonly used in holiday lights until recently. These lights produce a broad-spectrum white light, and are colored by coating the glass envelope with a translucent paint which acts as a color filter. Some early Japanese-made lamps used colored glass. Glow discharge lights Glow discharge light bulbs also can be used as holiday lights. The most common are neon, argon and mercury fluorescent lamps. They can glow in different colors, depending of the gas filling or the chemical composition of the phosphor. Neon lamps have a characteristic orange color, argon glow purple. Mercury lamps have most of the spectrum in the UV range, so their inner part of the bulb is covered with a phosphor, which converts invisible UV radiation into blue, green, yellow or other-colored light. LEDs Light-emitting diode (LED) holiday lights are quickly gaining popularity in many places due to their low energy usage, long lifetime, and associated low maintenance. Colored LEDs are far more efficient at producing light than their colored incandescent counterparts. There are two types of LEDs: colored LEDs and white LEDs. Colored LEDs emit a specific color light (monochromatic light), regardless of the color of the transparent plastic lens that encases the LED's chip. The plastic may be colored for cosmetic reasons, but does not substantially affect the color of the light emitted. Holiday lights of this type do not suffer from color fading because the light is determined by the LED's chip rather than the plastic lens. White LEDs are similar in most respects such as power and durability, but utilize a two-stage process to create the white (polychromatic, or broad spectrum) light. In the first stage, the LED produces one color of light, similar to any other LED. In the second stage, some of the blue or violet-blue is absorbed by a phosphor, which fluoresces yellow, imitating the broad spectrum of colors which the eye perceives as "white". This is essentially the same process used in fluorescent lamps, except for the use of an LED to create blue light