It would be a welcome addition if we could make a swatch based on another swatch, not unlike Sass (https://robots.thoughtbot.com/controlling-color-with-sass-color-functions).
In interfaces for example, I could create a green button with a darker green border. The darker green would be based on the original green and have the same hue and saturation, but the lightness would differ. That way, if I later change my mind and want to make all green buttons blue, the dark border would shift along.
I'm looking forward to your thoughts!