I just installed and re-installed IntelliJ. Every Java file is coming up RED. I checked the JDK; it is at 1.6.##. The maven clean install build worked just fine
maven clean install
I had the same issue, what fixed it for me was:
Go to File>Setting>Maven, I set the Maven home directory, settings file and local repo.
File>Setting>Maven
Go to Maven Projects and click on Reimport All Maven Projects
Reimport All Maven Projects
This did the trick!