[SWF hack tools] need help with background color

hi,
First of all here is a link for swf hack tools

http://www.swftools.org/swfcombine.html

this helps to add frames to an swf or combie two swfs in to one and some other.
I was just experimenting with it and i have come across this problem.
I have one swf with black background and another with green background . I used swfcombine and combined them and the output had the first frame playing in black and then the back ground changing to green in the second frame. Is it possible to hack the second swf and change the background color to white using any tool…Flex sdk anything. If there is any way please help.
Please dont tell me to open the fla and change the background unless there is no other alternative.