This sad, dark world...

[Arch Rogue]

I play EFU on low gamma (because it looks amazingly better) and have no issues. Use IG sources of light (torch, ultravision, darkvision, jewellery, light spell, whatever) if for some reason your eyes are failing.

[Incorrigible]

I can't see a damn thing at all in some areas at night either. Some are intentionally darker than usual, where during the day they look like it is night, and at night it is just pitch black. Nothing that can be done about that other than use the minimap to navigate and spam tab to try and find landmarks.

[sylvyrdragon]

I have to play with the Gamma all the way up, or I can't see a thing even in the day.  I think my video card is fubar though, or close to it.

[NoneButTheBrave]

I keep my gamma slider around 3/4 of the way up when playing because of darkness issues. I have also noticed that on my current PC, if I tab and return to the game everything will be tremendously darker. Re-tabbing does not fix this, but if i go to my video options menu, don't click anything just access the options and it will automatically get brighter and correct itself.

[Paha]

Those colour / darkness things are mostly result of your graphic card and driver, in alt tabbing. ATI and Nvidia look totally different in terms of lighting and colours with nwn.

Also, have you people tried adjusting your screen colours/lighting and then comparing it to just adjusting your game gamma.