Rover IDX allows Google Maps on your site to be styled using the Google Map embedded JSON feature. To add styling to your maps:
Log into WordPress on your site
Go to Rover IDX > Styling > Map Layout
Click on the Manage button for Google Map Styling JSON
Map styling allows unparalleled customization, for beautiful integration with your site colors and design:
Standard Google map of Chicago
Same map, with embedded JSON styling
Follow the Google documentation for embedded JSON style declarations. An easy way to quickly create the JSON is to use the Legacy JSON Styling Wizard. Paste that JSON into the Rover IDX "Google Map Styling JSON" textarea, and press Save.