Plumbago Lips

Plumbago Lips

What are plumbago lips? (Hidden Monster)? ۔

So I read the hidden monster and the girl always describes Andy's lips as soft lips, what does that mean? the color? Formation? What is Plumbago? I tried searching but found nothing! Thank you very much!

I haven't read Hidden Monsters, so I don't know what Plumbago Lips means. I know plumbago is a plant with blue flowers. This is another name for graffiti.

Plumbago lips

Plumbago Lips