Hi Alison,
I could be wrong, but my understanding is that the colonial units were the NZ raised ones such as the Waikato regiments as opposed to the British regiments which served here during the Maori Wars. I'm not sure your relative would appear in a list of colonial soldiers who received the NZ Medal. My GG grandfather also served in a British regiment in NZ and Australia and received the medal but I haven't found his name in such a list yet.
Others may know more.
Cheers,
Stephanie