RGB, HSL are really pretty awful color spaces to work in because they are not perceptually uniform. According to Adam Argyle, this is the year for css color: State of CSS - YouTube
as support for oklab, oklch and other color spaces will be supported by major browsers. We shouldn’t need to wait for all browsers to implement this, however, before we see support in Figma as there are libraries to help with extended color space support (in fact, there are quite a few figma plugins that add lch color support, so surely the figma team could also add this to the app).
Would you please consider adding support for more color spaces in your color picker? Also adding support for specifying the color space for gradients would be fantastic (Color Spaces for More Interesting Gradients | CSS-Tricks - CSS-Tricks)