Well, I'd probably use the BitmapData class (more specifically the draw method) to take a pixel out of the FLV - create a movieclip, add a Video object to it and use the movieclip to draw the bitmap. Once you have the bitmapdata, you can use the getPixel method to get the RGB value for a specific pixel.
General notice: from now on, I would like to ask everyone to put [AS2] or [AS3] (corresponding to the version of actionscript you are using on your project) in front of their post titles when the question is actionscript related! Please help us help you faster. Thank you.