My subject is wearing a black wetsuit. How do I change the background color to checkerboard so it's visible after removing the green screen? Right now the background is black and my subject is blending into the background.
Unless you wan't to export your movie with an Alpha channel, makes no much sense working on video track 1. Why don't you put your picture in track 2 and a solid color or another picture in track 1?
Anyway, you can see the Alpha or set a white background, better than the checkerboard: In the left button on top of the Canvas window, select RGB+Alpha, or set White or Checkerboard.