LCD / LED panel power consumption
I also measured the power consumption of my LCD monitors with a power meter at zero brightness. Dynamic contrast is off and to be honest, it's totally pesky so it is allways off anyway. After some hours I checked my measurements with the meter. 

Results:

My monitors consumes more power when displaying full white!

Dell P2414H monitor - AH-IPS panel with LED backlight measured at zero brightness


total white 10.0 Watt 
total black 8.5 Watt


Fujitsu Siemens P20-2 monitor - S-PVA panel with CCFL backlight measured at zero brightness


total white 30.0 Watt
total black 28.0 Watt


You may think that I mixed up measurement results, but it is not ! I dare everybody to measure his/her monitor and post results !

The claim that every LCD/TFT monitor consumes less with total white is untrue.

I cannot measure monitor with TN panel as yet because I haven't got. I will measure a TN monitor at my workplace and will post results.

Added info:

Fujitsu Siemens P20-2 monitor measured again with strobe effect youtube video:

When playing Youtube video "Black and White Strobe Light" full screen the consumption is 28.5 Watt average at zero brightness. The backlight have way more impact on power consumption. This monitor consumes 45 Watts (when display black) and 48 Watts (when display white) at 100% brightness. Full screen strobe 46.5 Watts.