Yes, it is possible to style the marker using marker.fillColor, marker.lineColor, marker.radius  and many other options described in Highcharts marker API.

https://api.highcharts.com/highcharts/series.line.marker


Additionally, it is possible to change marker symbol using marker.symbol option.

https://api.highcharts.com/highcharts/series.line.marker.symbol


Live example of styling marker using available options:

https://jsfiddle.net/BlackLabel/evr56gu9/


Live example of changing marker symbol:
https://jsfiddle.net/gh/get/library/pure/highcharts/highcharts/tree/master/samples/highcharts/plotoptions/series-marker-symbol/