When you change default display profile in the OS, relaunch the apps. They need to pick up the new profile at startup.
The Dell U2412 is a standard gamut unit, so Adobe RGB is the wrong one. sRGB is a better match. This is only for testing purposes, but it's much easier to evaluate if the colors are reasonably correct.
I can't see what you've been doing, so just to be perfectly clear - this is where you change the profile:
