how do I change the color of "Trails" in the particle editor?

Im trying to make smoke particles and the trales under effects it the particle editor seems to get me what I want but they always seem to turn up purple an I want them to be gray. But whenever I change the color selectors it stays purple. plz help.

Before you can change the color of the trail itself from the “Trails” section, you need to add a material. You can do this under “Renderer”, and add a material to “Trail Material”. Now you can also change the Color over Lifetime and Color over Trail.