Flash Background Color
I came across an issue last week where we wanted to dynamically change the background color of the flash animation we had made. We did not only want it to change colors, we wanted it to fade into the other color to get the right effect we needed. So after a lot of investigation, I determined that this was not possible with the actual flash background color, but there was a type of workaround. You just need to make a giant movie clip that would be big enough to cover any size or resolution computer monitor in the back of the animation. Then you can easily apply any tweens you want to that movie clip to make it do what you want. Then without resizing your initial flash piec, you can get coverage of the whole screen.
I did find a way to change background color without the tween and it only takes one line of Flash programming. You can use the opaque Background property on the root of your movie for an instant color change. Here’s a fun little tidbit I found out too. If you try to tween using the opaque Background property you will get dazzling results, if not a seizure. It seemed to just go through a kaleidoscope of colors until the tween timer was up and it would end on your desired color. I am guessing that this is due to this property using the alpha-numeric values for colors.