[old_tv_nut]

Defocusing slightly doesn't make the auto exposure work differently. When you defocus, insted of imaging bright phosphor dots on some pixels and the dark spaces between the dots on adjacent pixels, you spread the bright dot over several nearby pixels so they see an average brightness that is more like the average that the automatic exposure sees.

Defocusing is tricky to do just enough that it prevents bright pixel overexposure but doesn't degrade resolution. As stated by DTVMcDonald, if you adjust the exposure towards a darker picture, it will help the very brightest pixels not be overexposed. However, if your picture is sharp enough to resolve the phosphor dots, this will mean the picture will look darker on average.

Regarding white balance: if your camera provides a way to save a custom white balance, you could do that by turning the color down and capturing that setting on a black and white image. But I agree with the comment that the best way to handle this is to shoot in raw mode and adjust the white balance in software.