Styled maps allow you to customize the presentation of the standard Google base maps, changing the visual display of such elements as roads, parks, and built-up areas.
You can generate your own style by using the Google Maps API Styled map wizard. Once you've created the map style you want -> click on the show JSON button in the Wizard and copy the generated JSON string. Paste the code in the hotspots configuration (Map tab -> styled map field), save it and after you refresh the page with the map you should see your styled map.
If your styled map is not being shown make sure that you've properly copied the JSON string. If hotspots encounters an invalid JSON string in the styled map field, it will output an error in the browser console.