If your lips are the same color as your skin then they wouldn't be pigmented.
I think I remember reading that Angelina Jolie has really pigmented lips and she used to hate them when she was younger, so she would wear a greenish-gray concealer as lipstick.. yikes!
My lips aren't SUPER-pigmented, but they definitely have a noticeable color of their own. That's why I don't like to wear lipstick w/ more than a couple shades difference, because I think my natural color looks best on me! Mine are like a mauvy-pink, so I can just throw on some gloss and i'm good to go.