Okay, the general concensus seems to be that green is out.
Comments on black and white: I tried those, white makes it look like she has no lips at all but weird teeth, black makes it look like a gaping hole in her face where lips should be (even with light gray/dark gray tones).
It's a tie between blue and purple, since purple got a lot of voice on the board I decided to change the lipstick to purple.
Thanks for voting!