Colour is used to create mood and to highlight objects in a production. The positioning of the lights and choice of colour have a strong impact on achieving the required effect and mood.

Watch the video 'Colour mixing' with Lincoln Gidney as he discusses additive and subtractive colour mixing.

There are some important things to remember when determining the lighting mix. It firstly, light acts differently to pigment colours. While the primary colours of pigments are red, yellow and blue, the primary colours of light are red, green and blue.

As the three primary colours of light are mixed, they tend towards white light and so it is obviously pointless to mix them equally as they cancel each other out. Also, as green light creates a ghoulish colour on skin, tending to make everyone appear sick, it is a less frequently used colour, particularly on its own.

How light mixes to create new colours is very important, but equally important is how coloured light reacts to the pigments in the set and costumes, or in the actors’ faces.

Subtractive and additive colour mixing

Colour mixing is combining the effects of two or more lighting gels and can be either subtractive or additive:

• Subtractive - placing two different gels in front of the same lantern. Subtractive mixing is used to obtain a colour effect that is not available from stock or from manufacturers, although the wide range of available colours is so wide that the need for subtractive mixing is reducing. Combining colours in this way reduces the light towards blackness. The three primary colours of light (Red, Green and Blue) mix subtractively to form black (or to block all the light).

• Additive - focusing two differently coloured beams of light onto the same area (for example Cyc Floods). Combining colours in this way adds the colours together, eventually arriving at white. The three primary colours additively mix to form white, as do the complementary colours.