In light of some testing, I ended up making an expanded version of my old color set. Thank you for the support and please enjoy!
Saturation isn't perceptually uniform!
Keeping the same Saturation and Lightness doesn't necessarily make colors look equally bright.

Hence I made two color sets based on the OKLCH color space, which is designed to make Lightness more perceptually uniform, so that colors with the same Lightness value look equally bright to the human eye, regardless of their hue.
In the first color set, each color decreases in Lightness and Chroma as it gets darker, similar to how matte surfaces behave in real life!

In the second color set, each color decreases in Lightness but not in Chroma as it gets darker

It's even possible to work with Gradient Maps and attain perceptual uniformity. And not only can you go from one color to another, but also from grayscale to color!

If you're using gradient maps:
- Add a Gradient Map Correction Layer on top of your colors layer,
- Import and select one of my gradients.
- Set the correction layer Blending Mode to Color.
- If the target color isn't desired, perhaps you need to adjust Brightess and Contrast. Do so in a correction layer below the Gradient Map.
- If colors look "boring" that's because you need to add some hue shifting. Do so manually with a brush. Now it's easier because with my color set you'll have better control of your values,
Color Set
Gradient Set