You can add gridlines to your plot and change their color, style, and thickness.
User Interface Location: Options on the left panel in PTC Mathcad Chart
Release: PTC Mathcad Prime 5.0.0.0
Benefits and Description
There are several options for adding and formatting gridlines in your plot. Add grid lines on a per-axis basis at major and minor tick marks. Change the color, style, and thickness of gridlines to format the background of the plot to suit your needs.