blue flames versus yellow flames in the burner. that's the difference to coffee flavor?

these are two things that are not directly connected. The color of the fire is about the gas and air ratio of the combustion, not about sweetness coffee. Coffee is so sweet it's because Maillard phase reacts and caramelisation that happens during development in seeds, not from the type of fire.

the blue fire is indeed more thermal and cleaner because the ratio of fuel and air is more ideal. yellow or orange flames show imperfect combustion. so blue is better than efficiency and hygiene, but it has nothing to do with the exact same sweet flavor.

if you want sweet coffee: focus on the roasting profile, especially on the ZMaillard phase phase between temperatures around 150-196 degrees Celsius. Quite a development in this phase that ZzCF003Z. not at his type burner.

if there's a yellow fire in the burner, it needs mastenance: clean a jet of gas that may be clogged or adjust mixed gas and air. it's more efficient hardware issues, not an option for taste.