How would you explain a rainbow to someone who has never seen one?

Below, is a simple, clear way to explain a rainbow to someone who has never seen one.
A rainbow is like a soft, curved painting in the sky made of seven gentle colours. It usually appears after rain, when the sun is shining behind you.
Imagine sunlight as white light. When this white light passes through tiny raindrops still floating in the air, the drops act like little glass prisms. They bend and split the white light into different colours. These colours line up in an arc, forming a rainbow.
The colours usually appear in this order, from the top to the bottom:
Red, Orange, Yellow, Green, Blue, Indigo, Violet
(You can think of it as colours fading softly from warm to cool.)
A rainbow doesn’t sit on the ground; it’s not something you can touch. It’s more like a beautiful reflection made by light and water. It looks real, but it is actually created by the position of your eyes, the sunlight, and the raindrops—so if you move, the rainbow “moves”.