Ok, stupid me I have never heard it called a diffuser, my bad.
It comes in an unpainted plastic of some sort and is kind of a beige color. There are screws in the wheel well and a couple under the car attaching the valance to the original stock skirt.
I painted my CDC aggressive front spoiler and that valance with a stone chip resistant black paint that is easy to touch up. Originally my front spoiler was painted to match the car color but it got easily chipped from highway gravel/stones so I pulled it off and used that black paint. It works for me because all of my exterior trim is black now, all the chrome accents are gone.