As there is no mechanism for reading the current colours of the widget via code (except through an API call that returns the whole JSON definition for the project) then its not possible to know what colour settings have been set by editing the app.
The question is very similar to this one:
and the answer is also the same…
Give the app user a colour picker to set the widget colours (I guess multiple ones would be needed as there are on and off and background and text colours to set) and update the properties via code when these change.
Some validation would be needed to ensure that the users doesn’t choose the same text and background colours.
Pete.