This light painting was performed on the Badwater salt flats in . The bright white salt surface did a great job reflecting the colors.
I used a flashlight with three colors of LED light. During this single 30 second exposure I lit each color for close to 10 seconds while waving my arm around up and down (which traces a sphere).
This has been my most popular photo over on Flickr, with over 20,000 views and 1300+ favorites. It has also received nearly 10,000 notes on Tumblr (although I don't really understand how that site works).