Just be professional and, of course, yourself! Just like any other interview.
I've been to many CCO's where the gals working there didnt wear make up; as if they rolled out of bed. And who were bitches (I mean a mouth full of attitude) but for some reason, they continue to work in a CCO.
You'll be fine. If makeup (especially Estee Lauder companies) is what you love, let them know!