In operating Bunsen burner first open the gas tap then adjust the regulator depend on how many air you want to flow through your flame you will make a combustion and non combustion flame ... yellowish candle like flame are not usually use in lab or experimenting due to its dangerous gas its emit that can affect us combustion bluish like flame are commonly used it have three region when it comes to hotness of the flame the middle part of the flame is the hottest the outermost region of the flame is moderate and the innermost region near the barrel is the coldest ...