I'm not sure if this is a hardware or software issue, but hopefully somebody can help. I recently got a new Macbook Air, it's the 2014 1.4GHz i5 11" model running Yosemote 10.10.1. When hooked up to my external monitor (which is a Dell U2414H) via MiniDisplayPort, sometimes after sleep or the screensaver being active the colours on the external display go strange. If you look at my attachments the first photo is how it looks, the second shows my MBA display side by side for comparison, the third photo is how it looks normally, and interestingly the final one is actually a screen grab taken within OS X rather than a photo, which is why I think it may be a software issue. Disconnecting and re-connecting the MDP cable solves it, but I am concerned that my MBA is only a few weeks old and may have a fault. Has anybody else seen this issue before? Any thoughts on what could be the cause? I don't think it is the monitor or cable as I also have a Dell work laptop that works with the same setup just fine. Not sure if it's worth mentioning but I usually run the MBA in 'clamshell mode' while connected to the external display, not sure if that could be having an effect?