From early childhood, we’ve been taught to recognize the colors of the rainbow—red, orange, yellow, green, blue, indigo, and violet—using the iconic acronym ROYGBIV. We see them in nature ...

Rainbows have seven colours in total. The colours of the rainbow always appear in the same order: Red, Orange, Yellow, Green, ...

You can use a prism to split (or disperse) white light into a spectrum of colours: red, orange, yellow, green, blue, indigo and violet. Dispersed means that the colours are separated out.