High Definition CSS Color Guide - Chrome Developers
For over 25 years, sRGB (standard red green blue) has been the only color gamut for CSS gradients and colors, with color space offerings within it like rgb(), hsl() and hex. It is the most common color gamut capability amongst displays; a common denominator. We've grown very accustomed to specifying colors within this gamut.
https://developer.chrome.com/articles/high-definition-css-color-guide