The tail is a bit much. I would tone it down to a more natural size. I'm not sure I would keep the hearts and diamonds at the end of it, either. When it comes to designing OCs, less is more.
The fuzzy hooves draw all of the attention of the eyes away from the rest of the pony, and the color clashes with the pony's coat color. Purple is a really bad choice to go with blue. When picking colors, avoid picking colors that are right next to each other on a color wheel.
The eyes aren't too
bad, I suppose, but if you were going for multi-colored eyes, I would have gone for heterochromatic irises. The purple in them is still a bit of an issue.