There are situations in which it may be desirable to change appearance options for selected features in ArcGIS Pro other than color. This may be done to increase contrast to:
At the time of this writing, only color can be configured for point feature selection. However, there is currently an Idea in the Esri Community requesting changing point size: Option to change size of Selection (Point) in ArcGIS Pro
In response to a similar suggestion, ArcGIS Pro: symbology for selected polygons, additional selection options for polygons were added at Pro 2.7.