Press one of the number keys at the top of your keyboard. 4 (Fire display) is the default, I think. In the graphics options menu, that equates to checking "Effects" (the top one) and "Fire".
fire display doenst help- I dont use the fire display, i keep it on alt velocity, and the fire isnt red and slightly glowing- same with plasma- it went from slighly glowy red to this weird purple/white. gasses dont have that slight glow either. annoying. very annoying.