This little application can be used to pick an image apart and to get an breakdown of the colors used in it. Try it out here: https://zeroone3010.github.io/image-color-breakdown/
This may come in handy when you have got, say, a logo with a few distinctive colors. Sure, you could use any app with an eyedropper tool, but with this one you'll get all the colors at once (or at least the 500 most common colors, but that should be plenty).
You will also get a list of the colors in the order of appearance (starting from top left, going right, then down). This may come in handy if you've got, say, a picture of a gradient and you need to extract the color codes from it in order.
As an added bonus, next to each color name is a link to colornames.org where you can check whether someone has named that particular color, or name the color yourself!
Here's an example screenshot picking apart the old Windows logo, as grabbed from Wikipedia in PNG format:
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