ok, so last time i posted here (look forward a few pages for 'guess who') you all gave some great advice on how to improve, so i thought id start with the colour theory... now dont ask me why shes holding the knife.. that just sorta happened.. but as for everything else, and especially the colours, how am i doing?
The colors are beautiful, keep it up. =) The proportions are off, though. For example, her waist seems a little thin for her height and build. Her torso seems like it's being viewed from the front, and her feet seem a little bit small. Her eyes are a bit close together, too. But those are easy to fix. Maybe as you're working on the picture, you should use some reference. If you have the money, there are many virtual pose sites, CDs and books you could buy; if you are strapped for cash, there's still Google and Stockexchange (http://www.sxc.hu), and books are free to look. Google's not the best tool for reference, though; when using the images search it frequently comes up with a lot of irrelevant pictures, so if you use that, keep that in mind.
Other than that, it looks good. Keep going. =)
Color theory isn't about using rainbow colors, but more like understanding how colors interact with eachother, and the moods they create in certain combinations and by themselves, how color can be used as value, and so on.
in going with a flat rainbow composition, you've lost a lot of visual interest, depth, and lighting (among other things).
Pandyra covered the anatomy problems fairly well.