A color gamut is a dimension in which we define colors, and the color space defines how we define a color inside the gamut.

For example, sRGB is a color gamut that spans a range of colors, and Hex, RGB and HSL are the spaces available to explore the gamut.

and the sRGB gamut becomes inconvenient:

• The technology allows better colors (at least a wider gamut than allowed by sRGB)
• Dead grey zones between two points in space.
• inconsistent levels of lightness

So two units have landed. One is oklch:

• l controls the lightness, and measured in a range of 0% to 100%
• c is the chroma value, measured in decimals between 0 and 0.37
• h is the same old hue of HSL, in the same range of 0deg to 360deg
• / a is the alpha in the oklch.

The chroma limit value could be infinite, but P3 Iphone display and sRGB are limited to 0.37.

“Chroma refers to the purity of a color. A hue with high chroma has no black, white, or gray added to it. Conversely, adding white, black, or gray reduces its chroma. It’s similar to saturation but not quite the same. Chroma can be thought of as the brightness of a color in comparison to white.” — Cameron Chapman