Customize Google Maps
Navigate to the map region you wish to use to preview your style. Jump to a particular location using the Enter a location field in the top right. Select a type of feature to style in the Selectors panel. If you only wish to style the Geometry or Labels for the selected feature type, select the required Element Type. Select the combination of Stylers to apply to the selected feature type. Once you are happy with the styling of the feature type, click the Add button in the Map Style panel to save the style and create a new style to work on.
Google Maps Colorizr