You didn’t tell which inpainting algorithm you want to use (patch-based, single scale, multi-scale ?).
Something like this anyway should do the job :
$ gmic input.tiff --select_color 0,255,0,0 -inpaint[0] [1],9 -rm[1] -o result.png
Of course, this is a ‘minimal’ command line, you have to tweak the parameters of the command -inpaint according to your inputs and desired output.