RGB colorspace question

While working on

  https://github.com/gap-packages/hap/issues/115

I noticed that,

  convert foo.png -colorspace RGB foo.txt

produces different results with ImageMagick vs. GraphicsMagick. For
example,

  $ head -n2 foo-im-rgb.txt
  # ImageMagick pixel enumeration: 640,480,0,255,rgb
  0,0: (220,110,7)  #DC6F07  rgb(86.3157%,43.415%,2.84276%)

  $ head -n2 foo-gm-rgb.txt
  0,0: (239,176, 47) #EFB02F
  1,0: (239,176, 47) #EFB02F

(If you want the source image, I'm happy to provide it, but I don't
think this is at all tricky to reproduce.)

I won't embarrass myself by speculating. Does anyone know what's going
on with the different colors?