Buff Dundotte males aren't that dark... especially this time of year. Mine are a creamy light tan/off-white color right now.
He appears to be a tan/buff gene based bird to me, and my guess is a sun faded molting Brown, or Cinnamon, depending on which breeder you ask.
A Royal Purple is a grey based bird, same base color as a Pearl Grey, just less pearling. This guy's background color looks like a cocoa brown to me...
Is the stripe of skin down the back of his head a blue/black or brown/black color?