The colors seem pretty spot on, and the blurry quality creates a dreamy feeling. Only thing I could probably nitpick about the color is that the heart could probably stand out a lot more in its similarly colored background. Yet, despite these things done right, I just get this itching feeling that we could have something better.
I can't really tell how much show-accuracy you're aiming for, but looking at the style of your nose, I can be certain that you're going with your own way of drawing ponies. Well, the nose style seems pretty convincing. If you rotate this pic a little bit, it might show you something that seems pretty off. The top of show-style mare heads are generally curved exactly how you drew it here but provided that their heads are level. The eyes, nose, and ears suggests that Fluttershy is facing downwards, so if you rotate this head to make it level, the front of her head appears to slope down instead of being mostly vertical like show-accuracy. I cannot tell if this head shape was intentional, but it's not a head shape that seems aesthetically pleasing to me if we're dealing with one of the cuter subjects out there.
A really curious thing about ponies is that they were never drawn to perspective according to an actual three-dimensional subject. I would definitely recommend coming up with a way of stylizing horses in a way to have some likeness to FiM-styled ponies but can make actual sense in the third dimension. I think we fell a bit short from that goal here as what I'm seeing here is an eye that is frontal-view.... on a side-view head. Giving it a moment to know why I'm seeing this, I think I can say it's because the shape of the iris suggests a frontal-view eye. It is too circular. If the face of a circle is not directly facing you, then what it should look like from your point of view must be an oval.
Then lastly, I think there could be a better way to frame this piece. It feels uncomfortably cramped and it's even more so as Fluttershy's hair appears to be squished just so this could fit on to the canvas. We could have a larger canvas so there is much more room to the right. Fluttershy's eye is directing attention to the right and I believe it would greatly benefit if there was room in that direction to direct attention with.
Overall, a very good coloring job done but more skillful anatomy and composition could get us something even better.