Limited Color Palettes - Unwanted Hex Picker

We are attempting to limit color usage to our brand identity using the Color Palettes. Unfortunately, in a rich text editor field, if you highlight a piece of text and click on the "Foreground Color (A)", an option for "Add Custom Color" appears along with the library options that allows a hex code to be entered. This happens even when all color pickers are turned OFF effectively allowing users to bypass the color limitations.

Please remove the hex picker. You can turn on the pickers in settings if you need this.
Having a default picker defeats the purpose of limited color palettes.