This is my setup for doing smoke trails. The background is my black velour sweater. It's actually covering up my water drop setup. Dual purpose desk.;-)
These are my two flash guns - a Speedlite 430EX ll and a Speedlite 580EX ll. I have made a black plastic snoot for each to cut out any external light. The snoots are pieces of black plastic taken from a school binder and taped on to the flash guns. I set the flashes at 1/8th or 1/4 power. My camera settings vary. Exposure is usually at 1/200 and Aperture from f 10 to f 18. I'm still experimenting with settings.
It's also handy to have a desk light aimed at the smoke trail for better focusing. The one I first used is now broken so I have to get another.
I use my Canon EF 100 mm macro lens on manual focus. Turn on the music, pull up a chair, focus and click away.
For the colours, I play with all the colour sliders and quite often invert.