Mermaid Painting steps

This one's for a fantasy painting assignment at school. It really took me forever, literally days. The last night I worked on it, I pulled an all nighter. I'm still new at this painting thing, so I know there are more than a few mistakes
I kind of like the idea that each one of the mermaids is a different deadly sin. 
Black and White- Sloth
Red- Wrath
Aqua- Lust...
That wasn't the original plan but it kind of turned out like that 

The following are 3 steps I used to complete the piece. There are other steps of course but these are the 3 major steps.

-Thumbnails, Roughs, Preliminary sketches, comps and color comps (sketches with pencil, colors with Photoshop)
Final, full size pencilsBefore final painting I do an underpainting (my underwater underpainting was blue)

Then final Painting (acrylics)