History
Forsius Color circle
The arrangement of the color spectrum in a circle is generally attributed to Newton, but already in writings from 1611 by the Swede Forsius one encounters the colors arranged in a circle, that is almost 100 years before Newton did.
Isaac Newton
In the 17th century, Isaac Newton analyzed the composition of light. In a dark room, he sent a thin beam of daylight through a glass prism. The prism broke the daylight in a range of colors from red to violet, the so-called color spectrum. The order of the colors remained constant – red, orange, yellow, green, blue and violet. Newton operated with a seventh color between blue and violet, which is called indigo, a warm dark blue color. Today, it is common to operate only with the six colors, also called spectral colors.
Color vs. Colour
Color and Colour are diffrent spellings of the same word. The both mean exactly the same thing and both are correct. Color is the preferred spelling in American English, and Colour is preferred in all other English-speaking parts of the world. The word has its roots in the Latin word color.
I use color most by default, but visually i thing colour looks better.