The light gray canvas basemap in black via the -webkit filter
You can change the appearance of any basemap With CSS filters. This works mainly in Webkit browsers (Chrome, Opera) but also Firefox supports some of these filters. For more information visit: “Say Hello to Webkit Filters”, “Quick Tip: CSS Filters and your Esri Tiles” and caniuse.com.
This example is based on the Create a map sample of the ArcGIS API for
JavaScript and changes the Light Gray Canvas from ArcGIS Online with the
-webkit-filter: invert(100%) to a black style. See the styles.css for
details.