Different colors between Monitor -> Display
Both the LG 4K and 5K look great next to 2015 / 2016 MacBook and MacBook Pro at the angle you have photographed. You could try to set a custom color calibration curve for both displays to bring them closer, but the color shift you have photographed is very large. 

Also, be sure to set the contrast and brightness levels on the external display before you attempt software calibration. Lastly, let the display run for 30 minutes before attempting color calibration.