He said he received a call from a delighted Dr Sean Palmer, the chair of Monarchy New Zealand, who had read the Times-Age building would be participating.
"They have offered me these people, who will ring me at any hour, day or night, to let me know what the sex of the baby is."
Since it is the intention to spotlight the Times-Age building when its refurbishment is complete, he said he may keep the lights up - though not in pink or blue.
Dr Palmer said the nice thing about the project was it encompassed the whole country.
"There are towers and town halls, airports and bridges, fountains and sculptures. Even the iconic, giant, metal sheepdog in Tirau will be sporting a colourful coat."
Dr Palmer noted the project has gained global interest. The Kiwi idea has already been adopted in Canada, where the National Tower in Toronto and the Niagra Falls will be lit up.
While baby guessing games are buzzing, Mr Palmer said he's secretly planning for a late arrival of a baby girl, hopefully called Elizabeth.
"I think it would be very nice after 61 years of Queen Elizabeth II - and we will have some years with King Charles and King William - I think it might be nice to have a queen again.
Officials have said Prince William and Kate Middleton's child will be known by its given name and would have the title His or Her Royal Highness Prince or Princess of Cambridge. Additional reporting, APN News & Media
Participating landmarks:Sky Tower (Auckland)
The Cloud (Auckland)
Christchurch Airport
Larnach Castle (Dunedin)
Town Hall (Dunedin)
Toitu Otago Settlers Museum (Dunedin)
Wall Street Mall (Dunedin)
Tairawhiti Guardian Sculpture (Gisborne)
Town Clock (Gisborne)
Victoria Bridge (Hamilton)
War Memorial Clock Tower (Blenheim)
Wairarapa Times Age building (Masterton)
Gilray Fountain (Napier)
Christ Church Cathedral (Nelson)
Clock Tower OR Puke Ariki (New Plymouth)
Princes Gates (Rotorua)
Great Lakes Centre (Taupo)
Clock Tower (Te Aroha)
i-Site Dog (Tirau)
Digital Wall Wellington Airport
The Majestic Centre lights (Wellington)
Old Town Hall (Whangarei)
Victoria Canopy Bridge (Whangarei)
Opera House (Oamaru)