Does brass have different color choices for burial urns?

Hi, I was looking for brass burial urns since they're more affordable and I found so many different designs that will look beautiful in a cremation niche. They weren't all the same color either, which was not what I expected. These so called brass urns looked as if they were dark brown and one was red, while the other looked nearly silver. Are they still pure brass or has it been mixed with other materials?