Bsplayer

1-

Right-click the movie, go to 'Subtitles...' > 'Font...' > 'Color' and choose the color from the drop down box.

You should uncheck the 'Remember movie settings' option under 'Preferences' > General tab. This option usually overrides the settings you used before for your subtitles making them look black sometimes.

2-

Right-click the movie, go to 'Properties' > 'DivX decoder filter' or 'XviD Mpeg-4 Video Decoder' or some other video decoder that's being used at that time to decode that movie.
There you'll find the image settings controls.