(Settings/Desktop/Appearance) Custom Accent colour looses UX element
We have an array of pre-set colours for the Accent in the Settings/Desktop/Appearance menu. The last option in the array is to select a custom colour, which is indicated by a white "plus" and border.
I believe some form of UX element is supposed to be maintained even after a custom colour is set, but it isn't. This could make it un-intuitive for a user who later goes to change their theming, or one who had theming set by someone else, either by importing a theme or receiving a system set up by family or friends.
In the top half of this image I've selected a custom accent colour, in the bottom half the defaults are in place; this shows the difference.
The + should stay in the custom color selector. From here. There is also a unique selected state similar to selected wallpapers.
Maybe when a custom color is set, the "+" could be replaced with a pencil icon to indicate you are editing de custom color.