According to her biographers Margaret Lewis [1] and Joanne Drayton,[2] for most of her adult life, Ngaio Marsh divided her time between her native New Zealand and travel abroad, with frequent and often prolonged periods spent in England, where most of her detective fiction is set.

World War Two interrupted this pattern, obliging Ngaio Marsh to remain in New Zealand from April 1938 until June 1949, when she finally returned to England for another lengthy stay.

During this ten-year period, Marsh lived with her elderly father on the outskirts of Christchurch, continued to write, drove a Red Cross transport vehicle and began her dedicated project to develop a professional theatre in New Zealand, working with students from Canterbury University, directing, producing and touring plays around the country.

Now in 1942, Marsh decided to set her next two novels (Colour Scheme and Died In The Wool) in New Zealand, dispatching her series detective Roderick Alleyn there, to investigate wartime espionage.

Although Marsh published two further New Zealand-set Alleyn mysteries (Vintage Murder 1937, Photo Finish 1980), the two wartime New Zealand novels stand distinctly apart from her main body of detective fiction.

In New Zealand's North Island, near the fictional coastal town of Harpoon, the Claire family operates a guest house at the Wai-ata-tapu hot springs.

Meanwhile, Colonel Claire's brother-in-law, Dr James Ackrington, writes to Inspector Roderick Alleyn alerting him that Questing may be an enemy agent.

Son Simon Claire observes flashing Morse Code signals from Rangi Peak and feels Questing must be a spy for the enemy; soon after an allied ship leaving a New Zealand port is sunk.

Some people return to the guest house walking through the area of boiling mud pools and hot springs, while others ride home in a car, taking the road.

Falls leads a discussion at the guest house where he posits that Questing is colourblind, explaining many lies he told regarding colours because he rarely admitted this physical fact to anyone.

Dorothy Cameron Disney wrote in The New York Times that this mystery novel, “civilized literature”, excels on many aspects in a strongly positive review.

[4] The Illustrated London News wrote, "The only true detective novel this month is by Ngaio Marsh - and what a good one it is... as lively a tale as heart could wish.

She notes that the scene of Colour Scheme is the hardest to place, suggesting “Ngawha Springs guest house near Kaikohe, on New Zealand's North Island,” with a nearby port city as the most likely match.