Microsoft Office doesn’t have a theme change event in their VSTO API, so in order to detect the theme change, we need to monitor the registry key “UI Theme”. The key can be found in the following registry path: For Office 2013: HKEY_CURRENT_USERSOFTWAREMicrosoftOffice15.0Common For Office 2016: HKEY_CURRENT_USERSOFTWAREMicrosoftOffice16.0Common The value...