If you need an RGB codec, have you considered capturing to AJAs 10 bit RGB codec and then telling FCP to render in RGB? Perhaps this will help you. You will find the same problem with a Blackmagic card as they use the exact same codecs that AJA does, and those codecs are Apple's. What you are seeing is the YUV to RGB color space 'shift', you need to either correct it in FCP before export, or correct for it in Flame if it's possible. I don't know Flame's color correcting capabilities.