I have updated the script
It now saves as a LZW-compressed
;; Saves a 1-bpp TIFF file for each color of an Indexed image where that
;; color is replaced by white and the rest of the image is black.
;; The TIFF's filename is derived from the name of the bottom
;; layer of the original Indexed image. The RGB color values are
;; appended to this name, separated by hyphens.
;; An example of an output filename would be
;; The files (one for each color) are saved in same directory as
;; the original image (or to the GIMP invocation directory if a
;; new image.
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