We are building an outlook webapp add-in, and based on the user preferences trying to change the outlook read/compose surface commands icons. Is this currently supported ? If it's not, what is the suggested approach on, how to show two different icons in the command bar based on the selected color mode ?
Currently the feature you requested is not a part of the product. We track Outlook add-in feature requests on our user-voice page. Please add your request there. Feature requests on user-voice are considered, when we go through our planning process.