Well, it's impossible to tell from photos, and Koa and Walnut are both woods that get lighter in color over time. I would wager Walnut on the front peghead veneer though, looks awfully similar to the Walnut top laminate, and I'm pretty good at wood ID. Add a photo of the back veneer and we can see if it's more similar to the back laminate or the top laminate.
Now we can settle the mystery of the Walnut neck, since it's got a light wood too, I'd guess it either Maple or Birch, but hard to tell from these photos.
Thanks for posting the link there, Slawie - appreciate it!