The whole model looks a bit muted. what did you use to build up the highlights? adding white or grey to your base colors often gives a muted look. for the green, try a slight bit of yellow when you're building up the highlights.
The straps on the boots are getting lost with the rest of the boots. Perhaps a nice sharp line highlight on the top edges of the straps to help them stick out more? Or maybe make the straps a brown leather against the dark green boots?
The lips and the eyes look really nice. The rest of the face needs more contrast though. The highlights could come up a bit more on the cheek bones, I think.
One of the things that Sue will always tell people in her painting classes and at Paint & Take is to bring the highlights and the shadows to where you think they should be, then take them another 2 steps lighter/darker. You're seeing the shading and highlighting because you've been looking at the model and you know where you put what colors. When someone else looks at the model, they haven't seen all of this work, so their eye doesn't make the adjustments automatically. Since I've started using some of the exaggerated highlights (stick to the parts that should be getting the most light, of course), I think my painting has improved a bunch. Remember: finish the highlighting, then go 2 steps more.