RealFlight displays with a red and blue shifted double image.
If the aircraft and flying fields appear as a red and blue shifted double image, your video card is displaying in Stereoscopic 3D rather than standard 3D.
Stereoscopic 3D is an option found on many high-end video cards, and is intended for use with 3D glasses. Stereoscopic 3D creates an extra level of immersion similar to 3D movies. When you view a 3D game in Stereoscopic 3D without the proper glasses, you will see a red and blue shifted double image. Standard 3D is what you see with more traditional 3D games where no special glasses are required.
If you are using a GeForce video card, you can toggle Stereoscopic 3D off using the Ctrl + T keystroke while RealFlight (or any 3D game) is running.
If Ctrl + T does not turn off the effect you are seeing, please contact Horizon Hobby Software Support for further assistance.