Some of New Zealand's biggest and most noted landmarks, including Auckland's Sky Tower, will be lit up in pink or blue to herald the arrival of the tiniest British royal.

Monarchy New Zealand has announced plans for a vibrant nationwide light show to celebrate the birth of the Duke and Duchess of Cambridge's baby, expected in mid-July.

Among buildings to be lit are the Sky Tower, The Cloud events centre on Auckland's waterfront, Dunedin Town Hall and a sheep dog-shaped visitor centre made from corrugated iron in Tirau in the central North Island.

"That one's certainly going to look interesting, especially in pink," the organisation's chairman Sean Palmer told AAP.

"Not that I'm guessing colours or anything."

He said about 20 sites had so far signed up to join the festivities, with the display set to start at dusk on the day following the royal birth.

He wanted Wellington's parliament buildings to be involved.

"They couldn't be tempted though as they have policies against such things," Dr Palmer said.