Originally posted by Joe Dusel Thanks for all the responses. To be honest, I am not sure of the type of overhead lighting. The lights need to come on slowly to reach their maximum brightness. This is in an industrial space with high ceilings and large windows on the sides. It was some sort of retail space in it's previous life, and now it is used for community events. The projection screen does not seem to be the issue since I saw the problem in other shots which did not include it. Also, the color shift seems to be on just one half of the image in some cases.
The problem with a lot of man-made lighting sources, Joe, is that they're not necessarily constant. They may appear so to our eyes, but they could be pulsed and/or or show high frequency colour shifts that average out to an overall perception of one colour so far as the human eye is concerned. But shoot with a camera, and you're capturing a very specific point in time. You won't notice the difference through the viewfinder, but the camera's sensor does.
It becomes even more complicated if the sources of lighting are mixed types (as in this case) - especially so if you move just slightly between shots. My guess would be that the lighting through the window(s) may have changed ever so slightly between shots, but it's impossible to know without being there.
Of course, this can fool your custom white balance setting too, as that's also sampled at a specific point-in-time. But in this case you have an ideal solution, which is to set the white balance in post-processing by sampling the whiteboard