The classic smoke bomb, instant fire demonstration, and dancing Gummi bear demonstration all have purple flames. The purple color is caused by oxidizing the potassium salts used in those projects. If you sprinkle lite salt (KCl) on a candle flame or a fire in a fireplace, you can get purple flames without the smoke of the smoke bomb or highly energetic combustion of the demonstrations. Other potassium salts also burn purple.In addition to imparting a violet color to flames, potassium is the second lightest metal. The pure metal is silvery, but the element is so reactive, it's rare to see in pure form. Potassium spontaneously ignites in water and oxidizes very quickly in air.
More Potassium Facts
Photo: Potassium produces a characteristic purple flame in the flame test. (Herge)

Comments
this doesn’t work… ive tried it like 9 times and nothing happened… is there a special way i have to do this??
You need to be sure you are using lite salt that is pure potassium chloride and not a mixture of potassium chloride and sodium chloride. Also, it’s important that the fuel you use does not contain any sodium that would drown out the violet color with a yellow flame.
I’d like to have a purple flame come from my unity candle when I get married. Is it possible to have the wick weaved with potassium or some other additive to make this possible?