The Samsung Galaxy S II has not yet been officially announced in the States, which means that the Korean based manufacturer has time to fix the problem before launching the U.S. version of the phone, expected to be available at three of the top 4 U.S. carriers (Verizon, AT&T, and Sprint). You might recall a similar problem happening to the Apple iPhone 4 and Apple told those with a yellowish screen that the discoloration would eventually go away-which it did. Perhaps Samsung will simply parrot back Apple's solution to the problem of yellowing displays. If waiting for the discoloration to fade doesn't solve the problem, it will be up to Samsung to find out what is causing this and what the solution is to remedy the problem.
source: Xda-developersForum via Engadget