Will my painted metal roof fade?
As with all paints, there are different qualities of paint. For metal roofing, a PVDF or "kynar" finish is the way to go to ensure that your color will last. This is a manufacturer applied color coating with multiple layers as shown below. Many manufacturers warranty the PVDF color for 35 years.
Here is a link to a sample 35 year warranty for the PVDF coating from a local supplier.