Your questions require more information for a better answer.
On the top of it, one could say that electricity is the largest resource, as it requires electricity to run all the components that eventually feed the monitor.
How much memory is allocated/on your video card? Video "generally" consumes the most memory per "application," since all applications are reduced to 1's and 0's displayed on the monitor.
As far as foreground/background colors, you want high contrast, but not "overly" bright. This is why many users will select bright foreground & dark background colors over the reverse. Video refresh rate used to play a role and still can in older monitors (VDTs) but not as much in newer monitors (LCDs).
For ergonomic studies, search Google/Yahoo/etc for such things as: ergonomic study video display color study
Some links include: