Ideally you should profile the monitor specifically. However I would suggest you see if Dell has provided any generic profiles for the monitor. The characteristics of the MacBook Pro display and the Dell I suspect are very different so you'll need a specific profile for the Dell. You could turn on screen mirroring so you have the same image on both the Mac and the Dell. Do they look similar?I've had a look on the Dell support pages and can't find any generic profiles, that may help.