I am evaluating the trial version of WebCam Monitor to keep an eye on my backyard. I noticed that the trees in the backyard cause motion so I have used a mask, but the white colored mask is displayed on the screen. Can I remove it from the on-screen camera preview?

You can hide the mask area from the camera preview in WebCam Monitor. To hide the mask area, right click on the camera preview and select the Edit Camera option. On the Mask Area tab, uncheck the Show mask area on camera preview option. Note- Even if the mask area is hidden from the preview, it will still function as a mask and the motion will not be detected behind the masked region.