I may have tripped up on the subject when I posted a reply in this thread last week. The original poster said that he was looking for "Ivory" paint, and I am not sure this is the same as the white paint that is on my Bighorn and used by Heartland for their beginning years.
Anyways, I posted that I had read on the forum in an old post that Ford Oxford White was a close match to the original Heartland White, so I got a can of Duplicolor Ford Oxford White at AutoZone. I sprayed a small test area on the upper surface of the hitch overhang fiberglass. I found the dried result to be pretty close, but slightly, noticeably, darker than the original Heartland White. With some more nosing around the internet, I learned that there are actually 2 shades of Ford Oxford White, Ford color codes YZ and Z1. Looking at the color samples on a non-Duplicolor repair paint manufacturer's Ford webpage I can see that YZ (old Ford Oxford White) on top of Z1 (new Ford Oxford White) pretty closely duplicates what I see on the test area. So, I would conclude that the newer Z1 code better duplicates the Heartland White than the older YZ code. The problem is that the universally available Duplicolor doesn't make such a distinction (says it works for both YZ and Z1 codes) and looks more like the darker YZ code. Some of the specialty duplicate color providers online have slightly different paints for these 2 colors, instead of just 1 for both. So I am going to get me some of that Z1 paint and see how that looks. I will let the forum know.
Here is that other brand color chip page with the 2 Ford Oxford Whites at the bottom:
http://www.automotivetouchup.com/touch-up-paint/ford/2013/f150/