Kind of an odd thing but I wanted to have a UIViewController mimic a UITableViewController's grouped background, which is a funny sort of shade of grey. Essentially after looking at forums and not getting the right answer, I used some creativity to get it.
The first step, is to use a Hex picker app to get a sample of a UITableViewController's background color, which ended up being #d3d7dd. I then went to this website, which has a very useful tool in general, for converting Hex to UIColor:
The value that I came up with at the end, which I set the view controller's backgroundColor as is:
[UIColor colorWithRed:0.827 green:0.843 blue:0.867 alpha:1] /*#d3d7dd*/