In Appearance tab of block sidebar settings can be selected color theme for your map, available are different predefined color schemes to fit your website design better.
Google Maps themes
Using Google Maps provider you can insert also Custom theme JSON code to show your own unique map theme. Just visit following website https://mapstyle.withgoogle.com/, create your map theme and paste final JSON code into Custom theme option in block sidebar settings.
For Google Maps are available following themes:
For OpenStreetMaps are available following themes: