@julian@fietkau.social @hollo @thisismissem @julian@community.nodebb.org @dansup @renchap It'd need to be two colors - one for light mode and another for dark.
...maybe you'd need a corresponding text color too, for when the accent is used as a button background, etc. A light and a dark mode text color.
...and then again, many clients have multiple themes with different color schemes. It'd be hard to ensure the custom accent is legible on all of them.