Horns mutation creates two large horns growing from the centaurs forehead.  

Horns mutation coloration follows the centaur genotypes basecolor, and can slightly mimic the markings present. It can also follow the general rules considering cervine antlers.

Horn artwork presented in imports are the default ones, but you are free to modify different kind of horns to your centaur with uniquer customization item
However, customized Horns mutation needs to stay as two clearly separated horns. The amount of horns present cannot change.

Cervid centaurs carry their own antlers, and can get horns mutation just like other centaur types. If you choose to modify the mutated horns, you are free to move around their original antlers. Keep in mind, that this will also affect their hairstyles, and you need Hairstyler -item for big hair changes. Small hair edits to make antlers/horns sit naturally are fine.