Feature Request: Add ability to specify usage thresholds for coloring

[C0rn3j]

dfrs is kinda bad-color-noisy with default tresholds:

so is duf, for example:

but duf has a flag to modify them:

How duf does it is however still not perfect, my complex suggestion to tackle this properly is here: https://github.com/Canop/dysk/issues/18#issuecomment-1975176105