Nice mermaid!
Great design! I like chains(?) around neck and arms.
For colors it is good to remember about color harmonies like complimentary colors or triads. And you want to have your focal point (usually face) you will use colors that stand out the most (the brightest or the most saturated). As you go further from your focal point colors should be more toned down (?) like it should catch less attention.
I don't know how to explain it so here are Marc's videos on color.
I hope that helps. Can't wait to see finished design!