I've done a piece before this that also dealt with the idea of lipstick transferring, because my character Sharla always wears dark lipstick, meanwhile her romantic interest Miracle doesn't wear any. I'm a real sucker for mushy gushy romance stuff, and "obvious signs of affection" like lipstick transferring are endearing tropes in romance fiction to me.
This sounds like an odd thing to bring up, but I remember when I first watched Mrs. Doubtfire as a kid (I was nine years old or so), the only thing kid came out of that movie remembering was a scene late into the movie where Robin Williams is switching between himself and his Mrs. Doubtfire outfit, in a "wacky" moment, he forgets to take his lipstick off while he's meant to be himself. He plays it off that he had bumped into an ex, and it "transferred" onto him, and my little kid brain was like "oh dang, that would happen!" and I was so fixated on that but I didn't retain anything else from the rest of the movie.
So anyways, this is all to say I guess I was going back to my roots with this piece. I chose blue lipstick here because I've always loved it.