Hello Revit Community!

One of my coworkers is having an issue with colors on his screen. Our office is running Revit 2015, and on my coworker's screen red lines are blue, blue lines show up red, and the colors in the realistic model display are way off. Everything prints correctly, but it's making things difficult to show walkthroughs to clients on the screen when all the colors are wrong.

Is this a settings issue? Does anyone know how to fix this? Thank you in advance!