The examples provided on imagemagick.org are awesome! Let's work through a few with some fun photos! More cats == better!

Let's experiment with the coloring book example:

magick 20220914_160244.jpg \
          -edge 1 -negate -normalize \
          -colorspace Gray -blur 0x.5 -contrast-stretch 0x50% \
          color-in.gif

Let's use ImageMagick 7.

magick holocaust_sm.jpg \
          -edge 1 -negate -normalize \
          -colorspace Gray -blur 0x.5 -contrast-stretch 0x50% \
          color-in.gif
  # For heavily shaded pictures...
  #     #-segment 1x1 +dither -colors 2 -edge 1 -negate -normalize \