If you want that brilliant color that you see in all the boating mags that will match your dash then you have to polish that swimstep first. Then when you have coated it will have a really nice luster that matches the boats gauges and trim.
I would look into having it fusion coated since it will be exposed to the water and usage. Anodizing is a process where they dye the metal and it tends to fade and if it gets scratched you will see it.
I would check with Dana Marine they offer fusion coating.
I would love to see some pics of your products you made. Plus I am putting together a new company that is making the custom speaker grills etc..
Maybe we can do some business?