I disagree with everyone and have more precise sound definitions:
Dark usually auditioned in dark room.
Darkness helps to purify the power lines with no influence of bulbs and other electric supplies. The fridge can also be turned of for real Dark listening. Dark in video if TV is off.
Forward basically signifies of absence of music when you fast-forward a tape or CD searching your favourite place on the particular track. The same is with video.
Bright is usually when you're playing through the whole house lightened and with dishwasher, washer, dryer, fridge is on along with your stereo. In case with video or HT you bring up the brightness and contrast on your TV to the maximum.
Laid Back is when you want to get laid but still you listen to so nice piece of music that you sit back and enjoy instead of gettin' laid. In case with video or HT you simply sit back and watch someone gettin' laid.