pink screen when I switch on my mac
There is a problem after the latest update before yesterday. When I switch on my iMac, there is a pink screen before login to the desktop. Just half second then back to the normal white and grey color. I called apple care, they taught me to press shift key to login to the safe mode, however it cannot fix the problem, may I know if my iMac was damaged? Please help me, thank you.
iMac, OS X Mavericks (10.9.3)