Identifying a Simile in Nature Description

Read the following excerpt:

As soon as the sun dipped below the horizon, the sky burst into a kaleidoscope of colors, like an artist's palette spilling onto the canvas of the evening. The clouds rolled in, tumbling and swirling with the grace of dancers taking the stage for an elegant performance, each hue more vibrant than the last.

What is the main metaphor used in this excerpt?