Maps displayed on your website can be styled with help of Google Maps API - MapTypeStyler object specification.
See example of map which is displayed in various shades of gray.
The code:
[
{"featureType":"landscape","elementType":"labels","stylers":[{"visibility":"off"}]},
{"featureType":"transit","elementType":"labels","stylers":[{"visibility":"off"}]},
{"featureType":"poi","elementType":"labels","stylers":[{"visibility":"off"}]},
{"featureType":"water","elementType":"labels","stylers":[{"visibility":"off"}]},
{"featureType":"road","elementType":"labels.icon","stylers":[{"visibility":"off"}]},
{"stylers":[{"hue":"#0099ff"},{"saturation":-100},{"gamma":1.80},{"lightness":10}]},
{"featureType":"road","elementType":"labels.text.fill",
"stylers":[{"visibility":"on"},{"lightness":20}]},
{"featureType":"road","elementType":"geometry","stylers":[{"lightness":50}]}
]
The map:
The listed code should be set in: Administrator - Component - Phoca Maps - Maps - Edit a map - Advanced Settings - Map Styles.
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Google Maps™ is a trademark of Google Inc.