It depends on what you're going for - with the skin, I mean. If you want a more realistic look, remember that most shades reflect a little bit of the colours around them. In this case, bring some of that green right into the very edge area of the skin. Not everywhere, but in parts. If you can, make that layer slightly transparent, so as not to contrast -too- much with the original purple. Also, if this is a mermaid, and she's underwater - consider the light source. Are there reflections from overhead sunlight? are there weeds casting shadows?
Of course, if you aren't going for Realism, none of this applies. Good job so far, keep it up!