This is the image:
The light part isn't perfect white but FDFDFD
I tried:
old.png -fuzz 5% -fill red -opaque white new.png
but the white becomes black!
This is the image:
The light part isn't perfect white but FDFDFD
I tried:
old.png -fuzz 5% -fill red -opaque white new.png
but the white becomes black!
Your image is greyscale. Try making it colour first:
magick old.png -colorspace sRGB -fuzz 5% -fill red -opaque white new.png