JMK - here's how it works for me: I sit on my couch and watch a Blu and Ray. I don't futz with the color on my TV - it's set the way it's set coming out of the box. I watch a movie - I know the movie intimately in terms of its look, color-wise. If that color is replicated while I'm watching then the color on my TV is accurate. I know this, because other movies that I'm really knowledgeable about also have perfect color, whilst others don't - brown, pale, whatever. Then I look at a screencap on my iMac screen. If it's vastly different in color than what I just watched then there's something wrong with either the caps or my screen, and I don't think it's my screen since other colors seem to be accurate. I hear all the time that these caps are directly off the source, but obviously something is wrong somewhere - and it's no wonder there's a disconnect with some people saying the cap is accurate (mostly people who haven't actually seen the disc in motion) and those who say they're not (and there are plenty of people who say they're not). And then occasionally we find that whomever has done the caps has a setting off (sheepishly admitted, always - not saying that's you, but you've seen it happen). I don't know what it is exactly - I can only go by my eyes.
