Do you know what type of movie file it is (i.e. what compression-codec is used)?
Is "Use DivX4 decoder for ..(etc.)" selected in BSPlayer's "Options"/"Preferences"/"Video"?
Did you already have a look at the position of the color control sliders?
(Right-click on the video screen and try both options ("Color controls" and "HW color controls"))
(Or directly approach the decoder via Right-click and then select "Properties")