Color of Stage Lighting
Color temperature is measured in Kelvin, and gel colours are organized by several different systems maintained by the color manufacturing companies. The apparent colour of a light is determined largely by the gel colour given it, but also in part by the power level the lamp is being run at and the colour of material it is to light. As the percentage of full power a lamp is being run at drops, the tungsten filament in the bulb glows orange instead of more nearly white. This is known as amber drift or amber shift. Thus a 1000-watt instrument at 50% will appear far more orange than a 500-watt instrument at full.
LED fixtures create colour through additive colour mixing with red, green, and blue LEDs at different intensities. This type of colour mixing is also used frequently with borderlights and cyclorama lights to create different colours on stage and on the cyclorama. Another form of colour mixing is CMY, or subtractive colour mixing. Cyan, magenta and yellow dichroic filters are used in different percentages to create different colours. Because it is often difficult to create true reds and greens, a green dichroic filter is often added to fixtures using this method of colour mixing.