Saw your post on the forum, figured I could toss you some advice!
First off I'd like to say your piece is good, mostly good. You did a good job of picking values; the way the shadows are cast over the fabric of the clothes and background is definitely the strong part of this picture.
While your coloring is more than decent, the actual weakness of this drawing is in the linework. The way your character is leaning against the window suggests a certain perspective which is not supported by the background. The couch itself is rather isometric, and the background is very, very flat. This piece could gain a lot if it featured the same care for perspective you've shown in some of your other pieces!
The pose itself is slightly awkward, especially around the neck/right forearm area. The head looks rather small and the coloring on the face is very flat as well, meaning it could have used the same dynamic shadows you did so well on the clothing.
Finally, the overall unity of the colors could be increased. One would expect a moodier, blueish tint to this scene, especially with moonlight being the main source of light. Perhaps some color correction (blue soft light/overlay layer?) would have benifited the overall picture.
So there you have it! Overall strong coloring, but several composition/lineart issues to work out still. Keep practicing, and you'll be dishing pure gold one day! Always try to improve the next piece!