saveSelectedColor
Saves the currently selected color to the list of recent colors.
This method retrieves the color currently held by the PickedColor instance (which reflects the user's latest selection in the picker) and, if a color is set, it calls saveSelectedColor to add it to the persistent list of recently used colors. This list is typically displayed to the user for quick re-selection.
It is recommended to call this method when the color selection is confirmed by the user, for example, when a dialog containing the color picker is dismissed with a positive action.