I find it fun too.

For example, I was picking colors for a web page, and the cool thing is that you can pick greyscale colors pretty easily so that a light font looks nice on a dark background.

But I wanted purple buttons too. Using this picker, I could pick a purple that had the correct contrast with the background and the button text super easily, as well as light and dark variants just by setting that HCL luminance +/- 10 points. It's all about color contrast.

So if I changed my mind and wanted green buttons instead, I just need to move the colors I already picked over to the green column. And I'm sure to have about the same visibility against my background and font colors, maybe with some small adjustments.