Question: Pinto says, "The horse is not Black."
Sandy says, "The horse is either Brown or Grey."
Andy says, "The horse is Brown."
At least one is telling truth and at least one is lying.
Can you tell the color of the horse?
Answer:
The color of the horse can be any color other than Black and Brown.
If the color of the horse is Black - all are lying.
If the color of the horse is Brown - all are telling truth.
Thus, the horse is neither Black nor Brown.
If the color of the horse is Grey - Pinto and Sandy are telling truth whereas Andy is lying.
If the color of the horse is other than Black, Brown and Grey - Pinto is telling truth whereas Sandy and Andy are lying.
You must have noticed that for the given conditions, Pinto is always telling truth whereas Andy is always lying.