Trying to darken 6016 aluminum to "gunmetal" color?

I am trying to find a process or chemical that will darken 6061 aluminum to achieve a "gunmetal gray" This color is commonly found in many aluminum products but I want to achieve this finish myself. This will be used on car interior parts and needs to maintain the grain of the metal and not give ANY texture to the aluminum. These products are laser cut and I don't want to change the texture in any way, just darken. And it needs to be able to be touched very frequently and not fade or bleed to fingertips. Any suggestion? Thanks in advance,

It can be anodized and dyed any color you like. That will provide a very durable finish, however you can't do this at home. Take the parts to an anodizing shop.