I am currently designing a site and working with two different screens (laptop plugged into one or the other)
I worked all day with one plugged in and felt the site was too white. I therefore turned the desigin into a blue based background.
When I got home the white one was actually alright and the blue one was too dark. I therefore played with my screen luminosity and tried to make it look as white/blue as before and went from 70 to 80 in screen luminosity (not touched the contrast).
My question really is do you know what are the default factory settings for computer screen. Also are these figures tested across different makes of screens and therefore are they reliable i.e. 70 luminosity on one screen is not going to be equal to 60 on one screen and 80 on another.
I have two identical monitors (same make, same model, same size, purchased a couple months apart), both plugged in to the same computer, and with the exact same settings. One displays with a slightly yellowish-reddish cast, one is much more blue-white.
The only way to get predictable color is to have each user calibrate their own monitor. Expensive monitors can have more consistency than cheap ones, but they can express a great deal of variance, as was noted.
The answer is to use a design with "broad brush" colors. Depend on line and form more than color, and keep it fairly simple. Always have a fair bit of contrast between adjacent colors, unless you are deliberately seeking a smooth or invisible transition.
I test all my sites on a colorblind simulator [colorfilter.wickline.org]. There's no way to get colors that will appear the same to everyone, even on a calibrated system.
Embrace this limitation, because it will lead you to design more attractive and usable sites anyway.
All that being said, I use calibrated monitors on all my machines. I also calibrate my printers. However, this is not something you can expect site visitors to do.