Curved health bar

I would like to know how to create a curved HP bar in C# (Unity 5 pro) which is going to go around the mini map. Also the bar needs to change color depending on the hp percentage (if it's low, like 5/100 then it should be red, and if it's on full it needs to be green. And half way should be in the middle.) The bar should have a background bar which is static and the colored bar over it which shrinks depending on the health points.