How-to dynamically change color of the bkgd of the movie w/ btns

I can do this with movieclips, but as to getting the whole movie background color to change color via actionscript & w/ btns, and transition from color to color, like http://www.braingiants.com , aswell I noticed their movie resizes to the browser window, with the swf (in the HTML source) was set as
h: 100% by w: 100% aswell as “noscale” was on, I’m stumped, any tuts or coding examples or help would be great, I think I’m missing some coding or maybe I’m going about it the wrong way, AS wise.