For studying color, this came out very nice, you definitely accomplished the ends you wanted. The color contrast is the first thing I notice. There's also the details in her mane with the strands of hair that really accent the picture, as well as the flecks of leaves and lights around the background.
As far as the lighting shape goes, it does seem rather soft, and a little formless at some parts, which makes the fall off feel a tad inconsistent here and there. I'm slightly confused about the falloff on her back. I can tell the primary light source mostly comes from the right, slightly down, though the way it falls off on her back makes it look like there's a portion of her side that is oddly shaped. Conversely, I think the lighting on the ear might not be smooth enough, or that the inside should 'catch' a little more light as it's facing the primary source.
One thing I'd suggest around the eye is a little more definition around the edge as well, as well as a little more focus on the reflection. Making the reflection a solid color and then applying some glow to it. (I find eyes really fun to detail, so maybe I'm overestimating. 8D)
As far as anatomy goes, most everything seems acceptable given the style you approached. The eye might be a little big, but it doesn't negatively affect the piece really. Though, the nose seems oddly simple: giving it a little more concave feel as opposed to just a hole might look better.
And, again, I'm really loving the colors, especially with the tiny additional lightsources, as well as the mane, with the highlights and strands. Overall excellent work.
You were right when you said complimentary colors were used. It was amazingly done, for one, from the amazing shading and lighting that you did. You made this look almost 3-D for me, and the leaves in the background put life to the picture, as well as the mane and how much life it puts into it.
I love pictures like this, for it makes me feel almost as though it'll come out of the paper (or in this case, computer screen) to me. You did a truly amazing job on this picture, and that is actually a lot coming from me, because I'm one to where it's difficult to get me to say you did a damn good job, or put it in my favorites like I'll do with this picture after I'm done writing this critique.
Overall, this picture is the kind that I'd love to look at, and wish to draw myself eventually (though I'm not that good at art myself in my opinion), so I could appreciate my art as much as I appreciate this. This is actually saying quite a bit since I'm not exactly fond of Fleur myself, and I just love this picture.
An amazing show of imagination, to have even ten percent of your talent would be a dream come true... and yet I see this in scraps... huh... Anyway I shall be looking into all your work now, if this is anything to judge I know I wont be disappointed, well done!