Casio’s GA2100 series of watches — or the Casioak, as they’ve become known (for that squint-from-50-metres-and-it-kinda-looks-like-an-AP bezel) is a watch that has leapt from the realms of core Casio cultdom into something much more mainstream. Sure, the watch is a little faddish, but it’s undeniably fun. There are lots of options, the price is less than a big Swiss brand would charge you for a pin buckle, and it’s quickly spawned a sense of community. It’s also spawned a thriving cottage industry of customizers.

Chris Alexander’s home studio in Scotland resembles a miniature Casio warehouse. Chris, known on Instagram as @thedialartist, has a bustling business customising watch dials. From seemingly random space-like flecks on Speedmasters, through to intricate miniature paintings and even custom Girard-Perregaux dials done in collaboration with Bamford, it is one of those niches that make the watch world so fascinating.

Recently though, his work has been overwhelmingly dominated by Casios and rainbows. “I fell in love with the ‘triple black’ Casioak when I first laid eyes on the promo shots, and I quickly snapped one up. When it arrived, I loved the stealth look, but I was surprised at how quickly I became bored of it. Looking at the all-black face, I felt so much more could be done to turn this into something magical. It was a blank, black canvas and it screamed for colour.”

Inspired by the unobtainable rainbow bezel’s of Rolex, Hublot and even the actual Royal Oak, Alexander cracked his watch open, and decided to give his black Casioak the rainbow treatment. “I spent a while looking at loads of 12 segmented colour wheels trying to find the right balance to give me a clean spectrum of colour. If I am honest it has turned out better than I had imagined. I struggle to wear anything else.” And, a few Instagram posts (and a lot of DMs) later, we get to Alexander’s studio as it is today.

“It’s quickly turned into the most popular watch I have custom painted. For a while I was swimming in Seiko SKX007s and Datejusts. Now my studio looks like a Casio boutique. The only frustrating aspect is the lack of availability of the models. When I released images of my Rainbow Casioak, the triple black stock was almost dead and gone, so my pre-order list for this model has become a mile long.” But while the triple black might be the most popular model, it’s far from the only one — red, white, camo, purple and pink — for each version of model Casio release, Chris has a custom option ready and waiting.

Bright colours, and bezel aside though, what does The Dial Artist attribute the success of the model too? “It’s so thin and wearable. This is the reason so many others fell in love with the watch. It wears like a 40mm watch despite being 45mm due to the 11mm profile. This, and the oakiness.” All good points, but the fact that, with not a lot of money and a little wait, you can wear a rainbow on your wrist is a proposition that’s hard to beat.