With a video loaded: rightclick > Video > Color controls
(shortcut may also be a direct choice offered by the skin; this obviously depends on the skin used)
If nothing happens when using the controls, try if changing overlay helps: rightclick > Options > Preferences > Video
Try "Use overlay Mode 1" if that option is not already selected.
Then again check if you can change (i.a.) brightness (after having loaded a video .... rightclick > Video > Color controls)
Another possibility:
If you're e.g. using DivX5.x (movie must be loaded):
Rightclick > Options > Filters > DivX Decoder Filter
On "Quality Settings"-tab you can adjust settings of Brightness, Contrast and Saturation under Picture Properties.
(Note: "Yuf Extended Mode" must NOT be selected, otherwise Picture Properties will not be available)
(Similar for other codecs/filters; not for all though; depends on the possibilities of the codecs/filters themselves).
