They said it would be restful, relaxing and even brain-healthy fun. So why does my hand hover over the elaborate black and white patterns on the page, my mind in a mild state of angst?
In my brief experience as a colourer - 10 days - I've come to call this foreboding "the colourer's conundrum". It's the silent crisis over which colour theme to run with; which corner of your potential work of art to start in; coloured pencils or gel pens; and the fear of failing to stay within the lines. The pursuit of perfection can be discombobulating.
Others have warned me about "colourer's cramp" - the affliction that strikes those who rarely use their hands in this digital age to hold a pen.
I don't recall having this much anxiety hunched over a colouring-in book as a kid, but the artistic stakes seem so much higher when you're an adult armed with felt tips, feeling the pressure to post your motley masterpieces on Instagram.
It has grown beyond a fad, to almost crazy obsession. Book publishers around the world use the word "phenomenon". For three years it has raged in the Northern Hemisphere but the colouring tsunami only reached New Zealand around March this year.
Doubting its popularity here? The Nielsen weekly best-sellers list paints a pretty vivid picture - in the past month, nine out of 10 international non-fiction titles for adults sold in New Zealand have been colouring-in books.
Local bookstores repeatedly run out of copies of the big sellers - books with beautifully tactile paper stock and magical names like Enchanted Forest and Secret Garden, by self-proclaimed "ink evangelist" Johanna Basford, and Millie Marotta's Animal Kingdom and Tropical Wonderland. In Wellington recently, I was told how fortunate I was to be able to buy a box of colouring pencils - the city had supposedly run dry the week before.
Don't think it's simply a hobby for retired folk with plenty of time on their hands. A 20-something woman across the aisle from me on a short plane flight was contentedly filling in Cats: Colouring for Mindfulness. And workplaces in Australia are handing out colouring books to their staff to help them doodle away their stress.
I bought a book - and 48 shades of lead - to see how de-stressing it could possibly be. Instead I became a little distressed. The first few hundred pencil strokes were kind of therapeutic; my brain concentrated on nothing but keeping inside the lines. I switched off from buzzing Facebook alerts; when my husband phoned, I told him to call back later. But when it came to choosing the hues for something like a clump of toadstools, I fretted about being true to nature's palette ("what colour IS a barn owl?") and it erased some of the inky tranquillity.
So I looked to those who've become immersed in this kaleidoscopic distraction from their busy lives, and find out how they stay between the lines.
Auckland marketing manager Chantelle Thomas first picked up a colouring book after a debate with her French flatmate. "We were discussing whether adult colouring-in books were ridiculous," 31-year-old Thomas says. "I said 'Yes, they're ridiculous ... but I kind of want one'."
She vowed to never take her colouring to work, for fear of colleague derision. But when she crossed the ditch to her company's Sydney office, it was all laid out in front of her.
"They have a sharing table - with books, felt pens and pencils - where you can go and colour. If you're having a stressful day, you can take five minutes out, colouring in, and it seems to relax you. Things don't seem quite as bad as they did a few minutes before. It's probably better than a walk or a coffee."
No doubt there were a few copies of the Colourtation series created by Melbourne psych-ologist and neuroscientist Dr Stan Rodski, and architecture student Jack Dowling. After researching stress in Australian executives, Rodski found that getting them to colour in repetitive, detailed patterns produced a calming, meditative state. According to the Sydney Morning Herald, big Australian corporations like ANZ and Bupa have provided their staff with copies of Colourtation, and Rodski has been in talks to supply some government departments in both Australia and New Zealand.
A colourer for two months now, Thomas hasn't been tempted to join any of the myriad Facebook colouring groups where members can show off their WIPs (works in progress) or chat about where to buy the best pens. "I'm not sure about sharing my artworks online; if people hate photos of food, they're going to hate photos of colouring-in."
But she gets simple enjoyment out of spending an hour in the evening embellishing her books with big, bold colours. "It's a more peaceful hour spent colouring than looking at other people's Facebook statuses, thinking 'I wish I was on holiday in Hawaii'.
"I've tried a lot of mindfulness, meditation and rescue remedy. But this is a more fun version, where something pretty comes out the other end."
A clutch of celebrities have given it their stamp of approval - Zooey Deschanel, Nigella Lawson and South Korean boy band singer Kim Ki-Bum, who posted his vibrant Basford image for his 2.4 million Instagram followers.
Lotta Dann, Wellington author and blogger on her alcohol addiction and going sober, has also embraced it, posting her artistry on social media. Beneath a multicoloured Asian elephant on her Instagram page, she wrote: "I know colouring in is very trendy right now, but as someone who lives life 100% in the raw, and is always looking for authentic ways to relax and switch off, this really does work! It requires just enough concentration to push out mind chatter, and is quite creatively satisfying." She decorated a dragonfly in 20 minutes, "while chaos reigned around me in the form of small boys, nerf guns, rubber bullets and a puppy."
In 2011, Johanna Basford, a commercial artist and mother-of-one in Aberdeenshire, convinced publishers that her hand-drawn black and white illustrations would have a grown-up following. Her first book, The Secret Garden: An Inky Treasure Hunt and Colouring Book, currently sits at No. 7 on the Amazon US best-seller list (slipping from its No. 1 status in April) and has sold two million copies worldwide. Along with her sequel, Enchanted Forest, Basford has sold more than 6000 books in New Zealand so far this year, according to Nielsen BookScan figures.
But her reign as the colouring queen seems to have been usurped by Welsh artist Millie Marotta - almost 12,500 copies of her two books have been bought by Kiwis so far this year.
Nevena Nikolic, Nielsen sales and marketing manager, admits it's a surprisingly huge and global trend. "In New Zealand, we first noticed a spike in sales in March and April, and there's no sign of it slowing down," she says. "The books are definitely high-quality, on quality paper stock. There are obviously people who want to be creative, but don't feel creative enough to draw their own pictures." At the London Book Fair this year, she was invited to pick up pencils and colour a wall of black and white art. (By the way, you can now buy colouring-in wallpaper).
New Zealand artists are finally getting a slice of the action. Levin graphic designer Mitchell Manuel's book Maori Patterns is No. 4 on the best-sellers list for New Zealand adults' non-fiction and in its third print run. Manuel, also an award-winning actor and scriptwriter, creates his Maori geometric designs digitally.
Waiuku artist Jo Pearson's first colouring book, All Good: A New Zealand Colouring Book - released next week - has been chosen as the official book for New Zealand Bookshop Day on October 31. She's head judge of a nationwide colouring competition linked with it.
Over two months, Pearson managed to hand-draw 80 pages of images with a nostalgic Kiwi holiday theme - all while raising two pre-schoolers, working as a freelance illustrator and helping her husband, former Bracu head chef Dan Pearson, run his gourmet food business.
"There have been lots of late nights at the kitchen table and the sofa, and days down at the local library. It's been a whirlwind." Hardly sounds relaxing, and yet she says creating small, intricate drawings is her passion; she loves their black-and-white simplicity.
She consciously steered away from using words like "mindfulness" and "art therapy" in her book. "Because sometimes creating art can be really frustrating; even choosing what colour to use next. It's not always meditative." (Don't I know it!) "I just see it as something fun to do, so if people find it therapeutic and relaxing, well that's great," Pearson says.
Friends Cat Fawcett-Cornes and Maree Glading this week successfully funded their book, Drawing on Mindfulness - a Colouring Series of New Zealand, through crowdfunding site Pledge Me.
Glading, an Auckland gourmet pie entrepreneur, approached Fawcett-Cornes, an illustrator, with a handful of colouring books and an idea.
"You could draw these," she told Fawcett-Cornes, who is much like Pearson - a mother of two young girls, who helps her husband, Greg Cornes, run his city cafe, Goodness Gracious. With a "full-on toddler", she found her escape these school holidays at her aunt's farm on the Kapiti Coast, drawing native flora and fauna for the 65-picture book.
"I loved colouring-in as a child, but I was quite meticulous - didn't like going outside the lines. I love colouring with my kids, but I actually prefer to draw and paint," she says.
Mindfulness quotes will be scattered through the book, which can be bought on Fishpond. "Maree is into mindfulness, and I try to live more in the moment. We saw the books as being really good for anxiety, stopping you from overthinking things; and something to concentrate on that doesn't have a screen."
Art therapy has been around since the 1940s, and recent anecdotal studies have shown that producing art can help to transform the moods and cognition of people with dementia.
Nicky Baigent, a psychotherapist at Auckland's Lister Centre who uses art therapy, says a couple of her clients use colouring-in for "total immersion and relaxation". Her daughter - in her 20s with a 10-month-old baby - uses it to "zone out".
"Personally, I tried it and found it utterly boring. I didn't enjoy being pushed into someone else's idea of art expression," she says.
But she doesn't see this colourful trend as a bad thing. "It can be seen as a form of mindfulness. You're using your hands and your brain, and you can relax, chill out and forget your problems, which has got to be good. It's an escape from the digital world - until you feel you need to share it on Facebook."
When I next pick up a pencil, to give life to my turquoise and lilac barn owl, I'll remind myself to breathe. And that I don't have to share my psychedelic, blurred-lines objet d'art for anyone else's critique.