For a long time, I had lived with my two monitors of the exact same model (LG 27UK650-W) displaying noticeable different colors and text in one of them being much sharper than the other. They’re both driven by the same graphics card (an NVIDIA GeForce GTX 750 Ti) but one of them is connected with a Display Port cable, and the other one an HDMI cable. Several articles talk about making sure that they’re both using “Full RGB” instead of “Limited RGB” which you normally do in the Control Panel of the graphics card, and/or the settings of the monitor itself. I tried that and couldn’t get them to display the same, and interestingly, they were even showing me different options in the monitor settings (e.g. when selecting a picture mode, the Display Port monitor showed me a list of 10+ profiles to choose from, while the HDMI one only displayed 4, none matching the ones from the first one).
Today I finally found the solution! Turn off the “Use HDR” setting from Windows’ “Display Settings” window:
As soon as I did that (did I restart afterwards? I can’t remember, try that too if you need to) for the monitor on HDMI (the Display Port one didn’t even show me that setting), the picture mode menu in both monitors started showing the same list of options, I was able to make all the settings match, and now they look as close to identical as is practically possible without doing very detailed calibration.