ESRI has announced the release of the ArcGIS Vector Tile Style Editor, available in beta on the ArcGIS for Developers website.  The tool gives you a fast and easy way to create a custom basemap style.

By selecting an existing vector basemap, you can customize the layer colors and labels.  You can edit everything from fill and text symbols to fonts, halos, patterns, transparency, and zoom level visibility.  When you are finished, the styles are saved as an item in ArcGIS Online with a unique ID.  The map viewer or any custom application can then reference the ID to display the basemap.  Check it out.