Each input source can be used for green screen technology. With the Chroma key technology you can make any color transparent. In other words, a blue or red background would also be possible.

The typical green is often used because usually people don't wear this color of clothes.

Important for high quality is the absence of shadows and disruptions in the (green) background.

In the example below the green screen is not setup tight.  As a result not all green parts can be eliminated.

  • Click on the settings icon of the green screen source.

  • Select Colour Key in the left menu.

  • Enable Colour Key
  • Click on the pencil icon and click in the preview the color you want to mask.

  • Now drag the Chroma Key slider to the right.
  • Enable the Chroma key filter and drag the slider to the right until you like the result.

As you can see in the lower left corner, some parts of the green screen cannot be masked.

  • Now you can present this source on top of other sources via overlay or a multiview.

For more details : http://www.vmix.com/help18/InputSettingsColourKey.html