Answer:
If the horses with black hair have genes to produce offspring with chestnut hair, then it is entirely possible for to black horses to produce offspring that has chestnut hair. This gene may be from a parent, or may be a dominant feature in this species of horse.
Step-by-step explanation:
I did not have this lesson, nor am I largely educated on this, so I can not say 100% this is the right answer. If you use it please let me know if its right.