Why does my back up disk appear yellow sometimes and blue others?
When it does the auto backups, it turns blue, but sometimes I plug it in, and it only turns yellow and will not back up on command. Help?
MacBook Pro, OS X Mavericks (10.9.1)
It sounds like you're talking about an external hard drive. I'd suggest looking at the manufacturer's website and finding out what those lights mean. If it's only a few seconds of yellow, it could be the drive spinning up. You may also want to run Disk Utility, choose that drive, and run a repair on it.