Dual monitors aren't showing the same colors/display

So I recently got a second monitor so I can work with two screens at once. As I kind of expected, I had to calibrate the monitors so their colors, brightness and all everything else match each other. But how much I may try, I can't manage to calibrate them properly. Worse, both monitors seem to be calibrated from tests, yet they still don't match.

It's hard to explain what the differences are, so I included pictures of them in the attachments. Take in mind that they're photo's from my phone, since screenshots obviously wouldn't work.

The first one, monitorDifference_blackgrayOnSteam.jpg, is made by placing the steam client over the two screens. The left side is from the new monitor, which seems to be more dark green, and the right side is the old monitor, which seems to be more light grey.

The second one are monitorDifference_foxOld.jpg (old screen) and monitorDifference_foxNew.jpg (new screen), which are from with a wallpaper. The old one seems to be more dull and brighter while the new one seems to be more colorful/warmer (?) and darker.

Just for the sake of having enough information, the old monitor is an Asus VH222H which I have for almost two years, and the new one is a LG Flatron IPS224, which is just a few days old.

These differences aren't everywhere or not as noticeable, but there are plenty things like the above two examples where the differences are big and annoying. So the question is, how can I fix this difference problem and make the monitors match properly?

Some monitors have an option to adjust the black intensity. To me it seems that may be the key.

Dwarf said:

Are you using the sRGB colour profiles on both monitors?

It could be simply down to the age of the monitors - you probably didn't notice the changes with your old one until you hooked up your new one along side it. You might need to set the colour/brightness/contrast/temperature settings individually on one or both monitors to compensate for this.

What exactly are the sRGB color profiles and how do I check them (probably the settings of the monitors themselves)?

I'm aware it could be the age of the monitors, but I don't believe it should be as bad as this at this stage. I've been messing with the color/brightness/contrast settings with no result, though I couldn't find one for the temperature.

Edit: Actually, I just found the temperature, which I saw as the color settings. Sadly those didn't help either.

Edit 2: I found the sRGB color profile on the old monitor, and understand what you mean now. Using it makes no difference, and the new one doesn't seem to have it. Both are on the default manufacturer mode, and switching and matching the modes doesn't seem to improve it.

Erick Aguilar said:

Some monitors have an option to adjust the black intensity. To me it seems that may be the key.

I suspected it's something in that direction, but sadly I couldn't find anything in the settings for that.

You could try modifying the monitor settings with your GPU drivers as well.
I know ATI has that, but I don't know about nvidia to be honest with you.

I checked my nVidia settings, and it seems I can change my monitor settings with it. However, either it's not user friendly, or I'm too stupid for it. Either way, I'm not getting further with it than by using the monitor settings themselves.