I’m making an animated GIF showing some different color mixes for our satellite imagery. A GIF can only have 256 colors, so you want to make sure they’re the most important ones in the image – otherwise you get banding or noticeable dithering.
As I iterate on the GIF, I notice places that look bad and add little clips of them in true color to a palette image. Then I convert the palette image to 256 colors and tell the GIF converter to use only colors that appear in it. Thus this image has become a little scrapbook showing my priorities for color fidelity in the animation. Regions that I’m extra worried about appear more than once.