I recently photographed a delicious BLT Michael made but my photo looked anything but delicious. I mixed light sources, as I often like to do, but for the BLT it wasn't the right choice. By back lighting a subject with white light (sun light through a window) and using yellow light (tungsten bulbs) as the main source, and selecting the white balance on the camera for the bulb light–the white light turns blue–which I like because food is rarely blue and blue can really bring out the warm tones of food with out using a background or table cloth. But the day I photographed the BLT was rainy and gray day so the light coming through the window was not white, but a cold blue gray. The bread looked muddy gray and the bacon looked more gray brown then red. So Michael will need to make me a new BLT (shucks!) and I'll shoot again using different light sources.
Here is an example of when this technique of mixing light sources; this photo of garlic that has little color on it's own.