On this wood?

What wood cherry gives off a different color flame.

I think that was a piece of maple.

Is that driftwood, found on the beach? If so, some sort of minerals. If not, then probably just a very dry piece of hardwood that is burning very efficiently; I'll bet it's putting out very little if any smoke.

Use to be able to buy a powder to thro on your fire to make pretty colors. don't know if its still available. ca.1969.

It's still around. My kids demand it every time we go camping.

I've been burning some 2 year old locus and hickory and once they get burning and I close the damper down a little they look something like that.

I had to use old oak dock pilings once, once the salt gets in you can't really dry them out, but they sure burned pretty colors...lol

Take a short piece of 3/4 copper pipe and insert section of garden hose inside....throw it in your fire and it creates colors...kids will love it.

Your experiencing wood that has most of the impurities combusted, and has reached the gassing stage.

Green blue is getting there....All blue on top of coals is approaching a low 02, pure gas state.

Here’s a video for that full effect. lol

Nice!....Let it burn down, cut some air, and see if you get all blue on top of the coals.

I got the blues HT.

You may be getting a secondary burn off the gasses coming out of the wood. That is how a true rocket stove works, and why they get so hot. I am not sure a plain wood stove will gasify wood, but it may to an extent depending on the stove and wood.

Used to do this some years ago makes pretty fire. Not so sure best to roast the marshmallow over.
But I can't say thatI have looked to close for warnings on the powder they sell now.

Mac