Any way to create simple colour ramps for simple shading

[Autocrat Daddy Jones]

I'm trying to learn pixel art and, like many people, I'm struggling a little bit with colors and shading. One thing I often find my self wanting to do is to take a simple color and then create a shade that is, say, -20 on the value or lightness and then another one that is +20 on the same scale.

It seems like I've created a nice dark shade for my main colour and a lighter shade as well which I can now use to add lighting and texture to my image.

However, in a number of places, I've sen that when you adjust the value you need to also adjust the saturation - and this is where I get confused.

Is there a simple tool - ideally within aseprite - that can create this simple three color ramp for me based on a give middle colour?

I appreciate that this is probably something done better by "eye", but, for now, I'd like to be able to "cheat" a little on this while I get a handle on some of the other concepts I'm trying to grasp.

Hope that all makes sense!