The process would be an endothermic process. A process that gets colder would indicate that heat being is being absorbed in the system thus endothermic. Being endothermic, the energy that is needed to break the bonds present to hold the ions or the lattice energy should be greater than the energy that is released when water molecules would form bond with the ions or the enthalpy of hydration. Also, this system is driven by the increase in entropy of the system since as the salt dissolves, disorder in the solution increases which means the entropy increases which is a favorable change.
