Put it in the sun, it will purple up right away. Then put some sort of finish on it - we use lacquer. We have some purpleheart pieces in our house that have been up three years with no change of color from the original purple.
What Nancy said:laughing:, exposure to sunlight will make it purple again in a few hours....but too much UV exposure over time will turn it brown even black again. I would use a finish with a UV inhibitor if it is going to set someplace in direct sunlight.and if it was to age about long might it take