OKLCH really shines if you have to interpolate color between two colors (e.g. in space resulting in a gradient or in time as part of an animation) or you just want to change a color without makingnit darker or brighter.
If you interpolate between RGB colors you will get very weird grayish shades inbetween and the new color may be preceptually darker or brighter, which may be a problem (e.g. if it is text on a background). With OKLCH you define one color and as you rotate around the color wheel it stays the same preceptual brightness, which is incredibly cool.
This means before a designer would have to touch 3 values (RGB or HSV) to match the colors preceptually using their eyeballs, now there is only one value and it matched nearly perfectly as it is.
If you interpolate between RGB colors you will get very weird grayish shades inbetween and the new color may be preceptually darker or brighter, which may be a problem (e.g. if it is text on a background). With OKLCH you define one color and as you rotate around the color wheel it stays the same preceptual brightness, which is incredibly cool.
This means before a designer would have to touch 3 values (RGB or HSV) to match the colors preceptually using their eyeballs, now there is only one value and it matched nearly perfectly as it is.