I'm in the process of installing my EK waterblock. Judging from the things I'm reading on different threads in this forum, the backplate LED issue when a waterblock is installed is not yet fixed (again, shame on you EVGA for not fixing multiple issues with this freakin' expensive card!). I forgot to set the color to my liking before taking the card apart so I'm assuming that red will be the color of the backplate LED when I fire it up. It doesn't matter much because my GPU will be mounted vertically anyway but I still want to know are you able to turn off the LED completely with Precision OCX? Or should I just leave the cable disconnected? Or just do what the other person here did and connect the G and GND pins to the header only? Green is what I want, btw.
 
EDIT: I don't think Bombenfreak's idea will work in my case because the card has the LED set to Red in the first place. So I'm assuming the PCB header will not give 3V to either G or B pins.

heatflux
For the guys with water blocks who are still having problems...
 
Download the latest Precision OCX
Go to C:\Program Files (x86)\EVGA\LED Sync
Run LEDSync.exe manually and setup your LEDs
 
Worked perfectly for me!

Sir,
Thank you.
Many of the ones who have this issue may be pleased to finnaly be able to change the backplate led with this tip you gave.