I am doing a complete restoration on my car, and will be done this summer. I decided to go with the original iris blue on my car, too. I found out from other members the bottom was painted the color of the body. Unfortunately, I found this out only after I used black bed liner on the bottom. I do not plan on driving my car continually in rainy or snowing conditions either, but living in Washington State, I considered bed liner applied to the bottom and fender wells cheap insurance. It was a pain removing the old tar type undercoating, sandblasting it, spraying epoxy primer, painting it, and applying undercoating, but I considered it a must since I don't want to be underneath this car again doing repairs in my lifetime. The boot area was never completely painted from what I could tell. As a result, there was light to medium rust. I ended up sand blasting this area and coating it with epoxy primer. The entire inside is also painted iris blue. It was a very nasty job indeed. I have tried to keep my car as original as possible, but I admit I cheated here and there when it was clear the technology would keep my car better protected from the elements. Just my two cents.
Kevin