rainbow

A rainbow is an arch of colors in the sky that you can see in the rain when the sun is at your back.

Example: Traditionally, the colors of the rainbow are red, orange, yellow, green, blue, indigo and violet, but in real life, it's actually a continuous spectrum.

When something is rainbow, it is made up of many colors.

When you rainbow something, you make it into something that has many colors, just like a rainbow.