This could be caused by a couple of things: 1. It could be a stretching issues. Try zooming into the image and changing the stretch type in the display. 2. If the above does not help, it may be a graphics card issue. In the ENVI Preferences under Display General, change the "Use Graphics Card to Accelerate Enhancement Tools" to No. You might also restart the application. Then try to display the image. If the above works, then it might help if the graphics card drivers are updated on the system.