In working with some really bad blue screen video, I noticed that the pixels in the blue (but very uneven) background, almost always have a higher green value than red value. In the foreground objects, conversely, the red value nearly always exceeds the green value. So I went hunting for a filter or plugin that would allow me to select pixels according to the relationship between red and green. Unfortunately, I have found nothing. The Boris Pixelchooser allows for choosing pixels based on whether a pixel's red value, for example, exceeds a set threshold or falls within a range, but I can't figure out how to relate the value of red to green. It seems to me this would be a very useful ability in more than just blue screen work. Does anyone know of such a plugin?