TS2570: Mac OS X: Gray screen appears during startupLearn about Mac OS X: Gray screen appears during startup
Currently Being ModeratedApr 18, 2013 1:37 PM (in response to Fiona Chang)
Gray, blue and white screens at boot time are almost basically the same thing. OS X corruption or incompatible third party software installed into OSX itself (called a kext file)
You can hold the Shift key upon boot (wired or built in keyboard might be needed) and this enters Safe Mode which will allow you to copy your users folders off the machine to a external storage drive (do not use TimeMachine for this)
Run through this list of fixes, your likely going to see positive results when you finally get to do #8, unless the previous hardware test or disk utility SMART status says there is something wrong.