1. I created a site column based on the managed metadata type named color.
2. I changed the managed property owstaxIdcolor to refinable:yes.
3. I added the managed property owstaxIdcolor in the refinement Web Part and request it to be sorted by name in ascending order.
4. The order stays displayed by number in the refinement panel. It doesn't want to show by alphabetical order. I already have used it with success on other types of column. Have you experience the same effect? Do you know how to obtain an alphabetical order?