I'm having some trouble with my MacBook Pro Retina display.
When it starts up, the display momentarily shows strange colours in 'blotches' on the screen (see image). This just lasts for a couple of seconds before the regular login screen shows up.
Is this likely to be a hardware or software issue? I had a warranty repair on it about 18 months ago and since then the screws on the bottom keep loosening, so I'm not sure if this is connected.