The vehicle information pages on your website have structured vehicle data embedded in them. This data provides your vehicle information to Google in preparation for Google Vehicle Ads, to ensure Google can index your vehicles without the need to set-up a feed.
Google expects each vehicle to have an interior type and colour, however these values will be blank if not set in your Vehicle Details section for each vehicle (where you can adjust the vehicle make, model, colour and mileage).
It should be safe to ignore the email but we'd recommend simply adding those values for your vehicles.