Lighting at the ends of hair

Hello!I used exponential high fog to create a pure green background as a green screen based on the following link.https://forums.unrealengine.com/t/how-to-make-a-uniform-color-background/339787But there is an abnormal light around the hair.
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Can this be caused by diffuse reflection or The Groom system is not set up correctly.If anyone can tell other methods of making green screens, it’s also possible.We need to use as single a color as possible for video processing.Thank you very much!