Modding \"Critter FRM Workshop\" (Fallout 2)

Faced such a problem. Exported files from the program in 8bpp bmp format (for new animation). I prepared all the pictures, saved them in 8bpp bmp. I fill it back into the program with a replacement, and it knocks out a pixel rainbow with the outlines of what I did.
In short, looking at the requirements of the format, I noticed that you need not just 8bpp bmp, but 8bpp indexed bitmap bmp. I don't know how to convert to this format.