I just installed elementary os to an old iMac 24inch from 2007( core 2 duo 2.4 ghz, 4gb ram, ATI Radeon 2600 PRO ). It is a beautiful OS, everything working nicely so far. But I noticed an issue when waking up from the suspension. After waking up, the screen becomes faded. Please see the attached screenshot. It looks like it is using only small number of colors instead of full colors available. Please help me fixing this?