You can't do it directly, but you can fake it with XY graph results probe markers/annotations. Create results probe annotations at the desired point locations. Then edit the display of the annotations.
1. Turn OFF the Show Textbox option
2. Edit the color of the font to match the background color
3. Move the annotation to shorten the leader line to a near zero length
You will get a black circle drawn around the point used by the annotation. The attached PNG show examples. Each one has 3 annotations. XYGraph1.png has 1 annotation whose text is black, and 2 annotations whose text matches the background. XYGraph2.png has all annotations with text color matching the background.
Simulation Product Management
Product Engineering Software
Siemens Industry Sector
Siemens Product Lifecycle Management Software Inc.