cctvtec

Get yourself a ground loop amplifier (humbug) it looks to me to be a ground imbalance. Basicly there is a voltage diference from where the camera is to where the dvr or monitor is. It could also be that your video cables are running alongside mains cables. stick a multi meter on the cable and see what voltage you get point to point (you should have around 1v) hope this helps

This may not help you now but any others having ther same fault may want to check the cameras. More to the point you may want to check that the cameras are properly sealed up. Many cameras use a worm drive to open the iris and if dust gets into the camera housing it clings to the lube on the worm drive and the iris sticks causing the camera to go red.