I have a voice talent doing an intro video in front of a clean blue screen. It's a .mov video that's loaded onto Track 1, the main video.
I overlayed a .jpg image (have tried both a light background image and a dark background image) with no other image editing onto Track 2.
I added the green screen effect on the CLIP on Track 1, eye-dropped the very uniform blue background color (no blue in the talent's image), and adjusted the Fading and Threshold sliders to get rid of the background and eliminate blue edges around the talent's hairline. When I play that Clip, it looks fine. I see