There are two different sets of settings. Underneath Display>Screen Mode>Advanced Settings, you can adjust RGB individually. Aside from that, if you go to Accessibility>Visibility enhancements>Color adjustment>Personalized color, you have a different set of settings allowing you to adjust colors in a different way. I'm not sure that there will be more adjustability than adjusting the RGB settings of the LEDs.
It seems as though Samsung is trying to be stylistic instead of accurate with color. It's pretty upsetting as I expected better calibration with this phone. And if not that at least more detailed controls so the user could fix color. Instead everything seems dumbed down to 6th grade level.
Just bought a S21 (Base Model) a week ago and I'm also frustrated with the color profile as well.
I tried all the available color profiles through adb and trust me it won't make much of a difference. The adb options are just slight variations of 'vivid' and 'natural'.
I really do hope samsung do address this issue.