Hue is essentially RGB on a basic scale, Hue is the full spectrum of the colours (as bold as they can be). The angle on the color wheel (0–360°). Rotating hue changes which color the light is without altering brightness or vividness.

• Examples: 0° red, 60° yellow, 180° cyan.
• Lighting impact: Sets the tint the light casts on surfaces. Additive mixing means a blue light on a yellow wall trends toward green.

Saturation, which is how much colour something has - it's a scale of the colours relationship between greyscale & hue. Another way to think about it is the amount of white light mixed with the chosen hue.

• High saturation: Vivid colored light that strongly tints materials.
• Low saturation: Near-white light that adds illumination without overpowering surface albedo.

How light or dark the chosen color is, a spectrum of black to white. The amount of light intensity given off by HSL is directly related to this value. In practice this maps to how far the RGB value is from black in your engine and how much the signal pushes toward white in HDR/tonemapping.

• High luminosity: Colors wash toward white; hue distinction can diminish (overexposure).
• Low luminosity: Colors collapse toward black; hue can disappear (underexposure).
• Visibility: The same hue looks greyish when very dim but pale/whitish when very bright.

This is the most important value, because you can have a _light entity with a high light value(say 1000), yet it's colour could have a low L/V value, and it would give off barely any light. Also this is why when you select a light colour that is full white 255 255 255 (or 1 1 1), the light always looks overbright and doesn't look like it has the correct falloff.