No red

Check the pins at the end of the VGA adapter of the monitor (this is the cord that plugs the monitor into the computer). One of these pins may be bent and may not by connecting properly to your video card. You can use a very small flat head screw driver (such as one from an eye-glass repair kit) to bend back into place.

If all the pins appear fine, then there may be something wrong internally with the device and it should be sent in for repair.

what brand is this monitor btw??
is this a CRT of LCD display?
this is one of the most common probs with CRT monitors. loose connections are common. try whacking the monitor to see if this has an effect.