Subtractive and Additive Colour Mixing;
Combining the effects of two or more lighting gels is known as Colour mixing. This can either be subtractive or additive.
Subtractive is the placing of two different gels in front of a lantern. This is used to receive a colour effect, which is not available from regular stock. However, the need for subtractive mixing is becoming reduced as there is such a wide range of colours. When subtractively mixing the three primary colours of light - red, green and blue, forms black.
Additive is when two different coloured beams of light are focused onto the same area. When mixing the three primary colours it receives the colour white.
