you can burn anything, but it has nothing to do with the colors in the toolbox, rather the color of the object being burned. It just makes it darker. If you go over it a lot, it gets darker and darker until it hits black, burgundy, or plum, something around there.
To use a color, you have to use the brush. The nice thing about Burn is that it doesn't just plop a flat color on like the brush tool, it gradiates the color a little bit, so it really does look like setting something on fire and watching it shrivel away
any other burn tips or suggestions? I know there are a lot of options to get different effects