This is a controversial subject. The original gray was darker gray than most are using now, and the original red was a darker red than most are using now.
The Ford dealers in the 70's began selling the lighter (almost white) gray, the same as what was being used with their blue and light gray thousand series tractors. To compliment that, they were selling a more orange red than the original dark red.
The Ford dealers had also been instructed by the Ford company to paint all used tractors they had for sale with the blue color. It was supposed to make them look newer.
So, the story is a mess, and you get to choose whether you want to "be original" with the darker gray and darker red, or be more modern with the lighter gray and more orange red. But most of us agree that the blue is just awful and should not be on the N tractors. I have 3 of the big blue Ford tractors, and they look good when painted and clean, but in my mind it just is not right for an 8N.
Some of the other guys have found the colors they like, but I have used the lighter gray and red colors from the FNH dealer. Your tractor will look good either way.
Paul in MN