camera motion detection improvement

Every camera-based motion detection system I've used or are aware of detects motion using a simple algorithm of counting the changed pixels. And every one that I know of suffers the same problem, which is false positives caused when the sun moves in and out of clouds. Although there are a few tweaks applied to minimise this, it's still a big issue. What I've noticed is that the pixel comparison is a trivial one based on either RGB pixel values or intensity. A better algorithm would be to bias the value of the change per pixel by hue more than by intensity. So a person or animal walking over a surface changes the colour (hue) but a change in sunlight only changes the intensity. This would be a very minor tweak to a program such as 'motion' or 'zoneminder' but would greatly reduce the false positive rate.