I have a Voodoo Banshee and a Viewsonic monitor with no problems with brightness/darkness, colours or contrast.
Presumably it is the combination of particular monitors and cards that create problems.
Does your monitor have colour correction settings? ie 9300K vs 6550K- if so, it's worth trying things on the other setting to see if that improves matters. Making sure that Windows has the appropriate settings for your monitor (rather than just Plug and Play monitor) could also help.