Radrobx, it's a possibility you are noticing the Splendid Software by Asus :). Uninstall Asus Splendid from Program/Features then restart and see the dimming grayish yellow color which you are noticing am pretty much sure, it'll be much better as its a tool to adjust the screen and disliked by alot of people which comes by default in Asus OEM Software.
For the keyboard, Update to the latest drivers for Utility on Keyboard Device Filter Utility, and Chipset Intel INF Update Driver, also when you manually increase the light on the keyboard does that work?
http://support.asus.com/download.aspx?SLanguage=en&p=3&s=521&m=G750JM&os=&hashedid=yql3Rpr80XDgQJblIf you say the screen works perfect when it boots its basically the Asus Splendid messing the colors up, I personally uninstalled it from my JZ and have much better color on the screen then the default one which comes with the Asus Splendid Software when you get the laptop out of the box.
Let us know how it works out for you
🙂