I'm having this 2012 mac mini, with an 2.5g i5 chip and upgraded 4gb ram inside. And I'm on the latest mavericks preview system, and Lately, I was having problems with the my graphics.. It happened when I zoom the iphoto pictures in the full screen model, or to preview a png file, the color of the object inside the picture just went wrong. For example, if it's a orange object, it turns to blue in the first second when the preview window pops up. Any suggestions would be appreciated.