What is common today?
A lot of color naming conventions today use tints and shades, which basically mean how much white or black is added to the base color.
@red-darker-15 is red with 15% of black added.
This system relies on a base color to begin with, so the numbers are relative. @red-darker-15 and @blue-darker-15 are not necessarily similar.
Using Total Value instead gives you a global set of numbers that relate to every color on your palette, as well as considerably shorter names.
Furthermore, when creating a color palette I don’t simply add black or white to create the tints because it changes the color’s essence, reducing it’s saturation and changing it’s temperature. A darker red should have lower brightness, but also higher saturation and maybe even a small shift in hue.