For basic styling see http://api.highcharts.com/highcharts/plotOptions.bubble.marker.states.select (example: http://jsfiddle.net/bn5s18rv/). If you want to add an image using the renderer or similar, you will have to attach to the select event (http://api.highcharts.com/highcharts/plotOptions.bubble.point.events.select). If you need more help with this, feel free to contact our support. If you are using CSS styling, use the .highcharts-point-select class: http://jsfiddle.net/wtwj3o5b/. Again, for more information, please contact support https://www.highcharts.com/support.