Dell Monitors include a Built-In Self-Test which is a stand-alone test to isolate the issue with the Monitor screen.
[1]Make sure that the monitor screen is clean (no dust particles on the surface of the screen).
[2]Unplug the video cable(s)from the back of the Dell monitor and the PC. The Dell monitor should now enter self-test mode.
[3]Press and hold Button 1 for 5 seconds. A gray screen should appear.
[4]Carefully inspect the screen for abnormalities.
[5]Press Button 1 on the front panel again. The color of the screen should now change to red.
[6]Inspect the screen for any abnormalities.
[7]Repeat Step 5 and Step 6 to inspect the screen in green, blue, black, white and text screens.
[8]The test is complete when the white screen appears.
[9]Press Button 1 to exit the built-in self test diagnostics.
Same Troubleshooting Link : http://www.dell.com/support/article/us/en/19/sln128867
Check if the issue persists in diagnostics test as well, so that we can process a monitor request for you, incase it fails.