Greetings,
Are you sure its not the monitor, cable or your color calibration settings? If you decide to replace the onboard graphics with a stand alone GPU, ensure you buy one of the same generation for your CPU. There is no need to spend money for a higher end card if your processor can't take advantage of it.
Using the (AUTO) setting for first display device is also acceptable. Your choices are auto, disabled, force. If you have an issue, just change it to Disabled unless you plan on using the both on-board and stand alone GPU.