The “Gizmodo” site (http://www.gizmodo.com) says that Apple has released a statement to them, admitting the production issues with iMacs.
According to the site, Apple says “We’ve addressed the issues that caused flickering and yellow tint. Customers concerned that their iMac is affected should contact AppleCare.”
In February, Apple released the 27-inch iMac Firmware Update to address to address screen flickering/yellow tint issues. It was the second firmware released to fix the glitches; the first came in December. According to Apple, the 27-inch iMac Display Firmware Update 1.0 updates the display firmware on 27-inch iMac computers to address issues that may cause intermittent display flickering. You can obtain it via the Software Updates component of the Mac OS X System Preferences app.