Is there anyway to key out a black background in FCPX?

I have a very simple, yet mysterious question I hope someone can help me with!

I understand that I can use FCPX keyer to mask out/key out a clip that has a green background. Yet... what about keying out a clip that has a black or better yet any other simple solid color such as white, teal, purple etc?

Here's a reference video below of falling leafs as a quick example..

https://www.youtube.com/watch?v=OGjeX63d6KA&list=PLXBgYHTPZ0lK6Qz6XpB9kVrR1XIZ3HQs2&index=5

Essentially all I want to do is key out that video's black background so that all you see are the leafs falling. I'd then add those leafs with the black background key'd out above another clip in my FCPX timeline.

If FCPX by default is not capable of this... is there a third party plugin out there that I could download to help achieve this?

Thank you for whomever can help give me some insight on this!