So, you would use two different layers. One would be the person and the other would be their hair. It is very, very common to key parts separately like this.
You could push the colors around on a channel to pull a luma matte based on the green channel as suggested or use the Extract effect to try to pull a luma key directly. Either way, this looks like it should be pretty decent. Good thing the talent wasn't blond!
In the future, hopefully you can suggest to whoever is shooting your green screen to actually get the talent ON the green screen! lol
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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