Newton's Experiments on Colours

Newton knew that when sunlight is directed through a prism, it generates the colours on a rainbow.
To study this, he let a tiny bit of sunlight in a darkened room and dispersed it through a prism. After playing around by letting the individual colours through other prisms, he observed that when combining the red, green and blue colours, they would regenerate white light.

He called these the primary colours. And mixing any two of them would create the secondary colours - blue and green forms cyan, blue and red forms magenta and red and green forms yellow.

Of these, he noticed that magenta was not found in the spectrum of colours normally, so it was a mystery. This was later answered by Thomas Young in his theory.

He also noticed that red and violet were similar, so he twisted the band of colours to form a circle. This is known as Newton's Disc.