Yes, you can change the style of the overlay from the settings page.
You can change the overlay color and opacity. We are using a color picker to select the overlay color.
Also we can set an opacity level to the overlay. If the value of opacity is ’0‘, the overlay should be a transparent one. If the value is ’100′, the overlay should be opaque.
In the XYZ WP Pop premium version and in the XYZ Popup Script, we can upload an image as overlay and background.
This feature is available only in the premium version.