You're not getting the full lip color because the blending is only .5. That's why you can't make it darker. Even if you changed the lip color Value_2 from red to black, it would still be no darker than half the face color map value.

Increase the Blending value.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)