Lawrence decided he would work it out for himself.
"We bake all our breads in store, so I asked our baker, Pepa (Osmani) if he was up for the challenge. He's not scared of anything and within two days of seeing them online we had them in store."
Osmani and Lawrence used edible food colouring bought from Hobbycraft for their first attempt, making seven colours of dough. The coloured doughs are piled on top of each other and cut into smaller pieces that Osmani rolls into bagels.
"We didn't like the colours in the first batch we made, so we played around with them until we were happy," recalls Lawrence.
"It's a different technique to making regular bagels and you don't get every colour in each bagel," explains Osmani. "We still rest them overnight and then boil them before baking as we do all our bagels, but we bake them slightly differently."
The time spent colouring and rolling the coloured dough means that Osmani can't make as many as he can of the regular bagels.
"I can make 500 in two hours but it takes two of us five-and-a-half hours to make the same number of rainbow bagels."
He's been kept on his toes as customers for the Lawrence's Mill Hill and Radlett bakeries have gone mad for them. "We made 60 for each shop on the first Sunday we sold them and by the end of the day we had sold 600 across both shops. We just kept baking more," smiles Allie. "Initially we were only going to do them on a Sunday, but the kids have been asking for them in the week, so we thought we'd do 30 to 50 for each shop, but we are selling 120 to 150 a day."
The bagels, which taste like regular bagels, are still flying off the shelves and Lawrence is toying with the idea of flavouring them.
"They look a bit odd with smoked salmon on, but work well with cream cheese. We've been approached by other retailers to supply them and we're also thinking of other ways we could use them - in football team colours maybe."
He shrugs off concerns about the amount of food dye in them. "The food colours, which we are now buying from suppliers in large quantities, are all edible. Everything has food colouring in, from red velvet cake to smoked salmon, and there aren't huge quantities."
The effect of food colouring on one's health is matched by another bread craze that crossed the pond a couple of years ago and was picked up by another Jewish family-owned bakery business. Termed Frankenstein pastries by some, a number of doughy mashups have been created here and in New York including the Duffin - muffin meets doughnut and the original deep-fried doughy hybrid, the Cronut. The Cronut, a deep-fried ring of croissant dough, was invented by a Manhattan bakery in 2013.
When Jennifer Rinkoff, fourth generation member of the family working at 100-year-old east London bakery Rinkoffs, spotted the trend online, she decided she needed to make them. "I'd never tasted them but saw what they were doing and worked it out for myself," she says.
After a week or so of false starts, the determined Rinkoff eventually perfected them and trademarked the Rinkoff version, the Crodough. "It takes three days to make them; on day one we make the layered croissant dough, on day two it rests and on day three we cut out the circles, fry and fill them," she explains.
The Crodoughs are injected with a range of fillings, which include chocolate fudge, Nutella, salted caramel, custard or cream cheese and crushed Oreos. "They are flaky on the outside - like a luxury doughnut," says Rinkoff.
"We make about 200 a day and always sell out - people come from across the world to try them," she smiles.
Another baker who has breathed new life into old bread is Tami Isaacs Pearce, owner of Karma Bread in north London's South End Green. Isaacs Pearce, who offers a range of Jewish favourites, started baking her challah with a variety of flavours.
"Each Friday I bake regular challahs but also a flavoured challah of the week. It might be a simple cinnamon and raisin version, but I also take inspiration from festivals and from the seasons," she explains. "For Succot I added crushed raspberries, which gave gorgeous pink swirls to the dough, and for Rosh Hashanah, I added apples, pecans and honey."
For Purim she is planning challah rolls topped with date paste and poppy seeds: "They'll look like little Haman hats. I like to blend and bend tradition."
What will they come up with next? Dyed Danish? Purple platzels? Stripey rye bread? The mind boggles.
Karma BreadYummies DeliRinkoff Bakery
