Many customers ask us how they can make colored fog come out of their fog machine. To learn the answer, you need to know what fog machines actually do.
Fog machines convert Fog Fluid into aerosol form. Theatrical Fog consists of very fine droplets of Fog Fluid – nothing more, nothing less. These droplets are clear like Fog Fluid – not white. (They seem to be white only because they reflect the light that’s shone on them, which is usually white light.)
So, in order to get colored fog, you need to shine a colored light on the clear fog droplets. Then they will reflect the colored light rather than normal/white light.
The only way to create a self-colored fog-like effect is with solid particles, i.e. smoke. This can be accomplished through burning, or dispersing powder into the air. A company called Theatre Effects in Cincinnatti, Ohio (www.theatrefx.com) carries an assortment of pyrotechnic products that can be used to create colored smoke.
If you try to put something into a fog machine that will cause solid, colored particles to be created, you will ruin your fog machine. Similarly, if you add a colorant to Fog Fluid, in order to try to create liquid droplets that reflect white light as a color, it will a) ruin your fog machine, and b) not work anyway (due to the amount/concentration of dye that would be required in order to get a visible colored fog effect).
Unfortunately, when it comes to colored fog, coloring with light is the only solution.