colors change when opening in another program or in another Windows XP

Hello
How to make black objects black again? They are black when I open the image
in the HP program where the image was scanned and created. But the black
objects in the same image on another computer are not entirely black, they
have yellow edges. The file format is gif. The image is 256 colors (8 bit
color). How to change color of the yellow edges of the black objects to
black?
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