Are you asking about metal roof panels, or metal shingles?
85 years is a looooong time. I'm guessing prefinished galvanized steel will be the material used? Depending on the coating color, etc., there will be fading over time. Most kynar-coated galvanized steel noticeably fades within 20 years, and any scrapes, etc. will rust. Mainly an issue if you have traffic up on the roof regularly, or live in an area that gets hail or snow, as they will all result in scrapes, etc. And if you want it to stay on the roof for 85 years choose suitable underlayments and consider using stainless steel fasteners, as hot-dipped galvanized steel nails typically will not last that long.