How to trace a bitmap to svg in multiple colors:

Generate the PPM format from PNG:

  convert download.png download.ppm

Generate a mask file for each color of the file:

  ppmcolormask "#184d47" download.ppm > download-mask1.pbm
  ppmcolormask "#66462C" download.ppm > download-mask2.pbm

Then trace the bitmap (bitmap -> svg):

  potrace --flat -b svg download-mask1.pbm -o download1.svg
  potrace --flat -b svg download-mask2.pbm -o download2.svg

Extract a list of colors from an image:

  convert download.png +dither -colors 10 -unique-colors txt: