Lots of different experiences. For me initially a flame, mostly orange, and as the tunnel refractory heats up this will change to a roar of mostly an orange gas-like fireball, with sparks. This would typify about the first 1/3-1/2 of the burn of the wood load. Somewhere around that time the "flame" starts to turns to orange-blue and then blue, with a constant roar. As the wood load turns to mostly charcoal-like material, even the blue disappears and all I hear is a roar, with sparks, and essentially no color at all. Both CO and H combust with a colorless "flame," so I would conclude that the later part of the burn is combusting mostly pure carbon to CO and CO2 and H to H2O. Chemists may have a more accurate description. I can't say that I ever see any smoke in the refractory tunnel area, although in the cold start firing I am sure there is some smoke. For a cold start I fire with the bypass damper open until flue temp reaches 350-400F, then close the damper, and what follows is near instant gasification flame into the refractory tunnel and the burn is off to the races.
My Tarm has a round sight window looking into the refractory tunnel and it is easy to see what is going on. If I open the lower door with the fan "on" the sound of the roar and visibility of the fireball is intense. I would guess the extra 2ndary air with the door open changes what is going on in the tunnel area.