Add some rainbow to your fireplace with Rainbow Flame Crystals. Ooh, or how would this rainbow light show be for your outdoor fire pit!? Just sprinkle these crystals on your fire place, wood stoves or campfires — the colored flames last for about 10 to 40 minutes.
Check out this Scout Master's Amazon review:
At the campfire this product produced some very nice blue, green and ever so often purple flame, which both the kids and the adults found very enjoyable (hint: don't tell them that you're using this stuff, especially the kids). The effects lingered for some time, about five minutes per heaping tablespoon of product. I found that a larger amount — maybe a half cup — was the best way to apply the product to a large fire.
Also, it's better to sprinkle the product throughout the fire, rather than pour it in so it piles in a single location. Dispersing the crystals troughout the fire will create an instant and thorough color flame effect, while pouring will get you an instant effect in a single location, with a pile of crystals that becomes somewhat self-insulating. Once a log falls or you stir the coals, and that pile of crystals is disturbed you will get another burst of color, which actually is a pretty cool effect, giving you shots of color hours after you've applied the crystals.