[pweasel]

i used to have the same problem as you. There are several independant things that set the color and hue and whatnot of a movie while you are playing it, both hardware and software. From the hardware part, (in my case of nVidia drivers) you go to display properties > settings > advanced > color management, in the dropdown select 'overlay' and set the brightness and hue as desired. That takes care of the hardware portion of this exercise.
The software ranges from the video settings in bsplayer, any Directshow filters configuration that you may be using (ffdshow for example) and codec settings.

you should go one by one checking the brightness in everyone.