https://www.esri.com/arcgis-blog/products/imagery/imagery/creating-a-grayscale-version-of-any-arcgis-online-basemap
Creating a grayscale version of any ArcGIS Online basemap
By Rajinder Nagi, Esri Cartographic Product Engineer We recently got a question on Ask a Cartographer in which Julie asked if you can ...
creating agrayscale versionarcgis onlinebasemap