Painting Brand New Painted Steel

Hello, I am installing exposed fastener steel roofing/siding panels on the walls inside of a garage bay. The steel is new and already painted but I need to change the color. I have a bucket of Sher Cryl 1300. My questions are whether I need to prime this material before applying the Sher Cryl 1300? The material is brand new and will never be exposed to the elements. If I do need to prime what should I use? Pro Cryl seems like the best choice but I was hoping to go a bit cheaper.

Thanks