What year did they start with the white roof?

[SS Tim]

Yes even in the six years we are talking about the sales names changed a lot but the codes stayed pretty consistant. There were changes and the Dark Blue comes to mind as having gotten a lot lighter for 71-72 than it was in the earlier years. The paint companies numbers are the biggest tell to differences in the tints. Here is an example I did showing the yellows used in Chevrolet cars and trucks some are close enough that you would think they were the same colors but in fact they are different.

But coming back to the ivory and white they were two diffrent colors with the ivory being a little muted. tended to complement the primary color vs the stark contrast of the true white.