I've been trying to do some vector tracing in Inkscape, but haven't been able to get it to pick up big contiguous sections of color like that. Do you have any tips, or remember what settings you were using?
I actually only use Inkscape for the lines; for the flat colours, I opened up the transparent .pngs in GIMP and went from there. I wish I knew how to make flat vector fill areas of colour as specific as this, that would make using Inkscape a dream. Sorry I couldn't be more helpful!