Colour range in Avisynth

Hi, I'm wondering whether there's a filter for avisynth which detects only grayscale colours in an image and removes all the rest of colours in it.

For example, I have some images with black and green colours. I want to detect only the black or gray colours, and remove the green.
I can do that in photoshop, but I have a large amount of images that need to be processed like that.

I've read that Layer Filter can do that, but I can't find it anywhere.

Any help would be appreciated. It doesn't matter if it's not an avisynth filter but another software.

Thanks in advance.