sRGB is the most widely used color space and is the default for most systems, and noticeably the web. It was proposed in 1996 as a standard color space of the web. sRGB was designed to match the average CRT monitor characteristics at the time.

Wikipedia: sRGB chromaticity diagram with Luminance Y set as R + G + B = 1

Short-coming

The sRGB color space lacks many of the color visible by the average human eye (limited gamut). It also lack perceptual uniformity, meaning that changes in the color’s chromaticity also change its perceived lightness 1

HSL vs LCH rainbow. Notice that the perceptive brightness change drastically in HSL

Footnotes

  1. Color Everything in CSS