Well you just visualising the pieces, so each piece is colored with a random color. This won't affect your render. You can turn of the visualise pieces or put a color node and make everything white for example.

Also you could review your fragmented model with the exploded view node.

I hope this could help you.

Try to play with the final density scale. It appears like the volume have more density in the black part of the pyro sim. Could be the emission because as you can see your emitter sphere is black in thr render image instead bright yellow/orange. Another thing could help you: use the temperature as emission field.

Let me know if you can fix it, and thanks for share

Amazing! I like the way you present your fx skills, its just hypnotic