When to Use HSL Over RGB for Design Work
HSL is generally the better choice when you need to programmatically or manually lighten, darken, saturate, or desaturate an existing color while keeping its base hue recognizable — since adjusting a single HSL value (lightness or saturation) achieves that cleanly, while achieving the equivalent effect in RGB requires calculating new values for all three red, green, and blue channels together.
As covered in the HEX-vs-RGB-vs-HSL guide, all three formats describe identical colors — the practical difference shows up specifically when you need to adjust or generate variations of a color, not when specifying a single fixed one.
Generating a consistent color palette
Starting from a single hue and generating a range of lighter and darker shades (for a UI's hover states, or a chart's color scale) is far simpler in HSL — hold the hue and saturation constant and vary only lightness — than working out the equivalent proportional changes across three separate RGB channels.
When RGB or HEX is still the more natural choice
For simply specifying a single fixed, final color — a brand color, a specific approved shade — HEX remains the more common and compact convention, since there's no need for the adjustability HSL offers if the color itself isn't going to be programmatically varied.