Применительно к видео? Кем, честно говоря, точно не знаю. Когда? Примерно в начале 70-х годов 20-го века.
Timing of the electronic switch is adjusted by the variations in light along these
boundaries. The process requires very strict control over the lighting conditions.
Towards the early 1970s, research began with systems in which the electronic switch
is controlled by colour variations (hue and brightness).
This technique - known in television jargon as "chroma-key" - has since become one
of the most widely used in colour television production.
Blue is often the colour used, as it can easily be avoided on people and sets, although
other colours can also be used (orange or yellow for example) to contrast better with
the chromatic composition of the scene.
The application of these processes can be repeated or combined, for example by
recording a scene already containing special effects with the addition of a new one.
Это отсюда
http://chem.ch.huji.ac.il/~eugeniik/history/tv_history.pdf
Вот тут еще любопытная статья одного из создателей Ultimatte (аппаратного, а не того, что сейчас называют AdvantEdge
)
http://www.gregssandbox.com/bs/kertesz.htm