@mat200 - I posted a reply in your thread.
I'd still like to know why any (or all) of these hi-rez cameras go to B/W at night with the IR filter switched out. One possible reason - in a night, low-light situation you may have mixed lighting (white led, incandescent, florescent, etc) and the camera can't get proper colors or white balance without the IR filter, so rather than deal with customer complaints about color the makers just go to B/W for low-light / IR filter situations.
One way to fool the camera and see what color-mode no filter looks like is to take a camera, disconnect IR motor drive when camera is in night mode and then switch the camera to color. The camera will think it slid the IR filter back in place but it won't be.
The 4239 apparently has a fixed IR filter. Has anyone checked to see if there is a drive/slider mechanism for the filter in that camera - but maybe it's not connected? Might be able to move it in/out with the right external signal.