The change came in part to counteract the 22-year-old's premature silver hairs emerging; in part to inspire his repeat quest for gold.
"I came up with it about a week ago. I figured I didn't want to do it when I'm middle aged so I might as well do it now.
"It was only fitting I need some extra style points. Maybe if I paint my hair gold I'll get another gold medal."
Over the past three years Nyika has packed on 10 kilograms to make his new weight class.
"The main difference is everyone slows down and I've sped up. I'm feeling fast and fit."
At first, moving from the 81kg division to 91kg wasn't an easy ride. Eating was a chore; training incredibly taxing.
With the guidance of strength coach Shaun Paterson, Nyika piled on 12kg in five months.
"It was a lot of time under tension strength training in the weights room. That was my least favourite type of training. I was throwing up after every second session."
Training centred on the German volume theory; slow movements, low weight, high reps. Lactic acid build-up makes for excruciating sessions.
"It's pretty horrible."
Nyika has been comfortable in the heavyweight division for three years now but his diet contrasts that of his team-mates, most of whom are shredding to remain under respective limits.
He woke this morning at 92kg, and by not drinking before bed can easily drop down to where he needs to be come competition day.
Others, though, can't enjoy the buffet at the athletes village.
"I think I'm the only one here who can actually eat breakfast properly. I had donuts for breakfast which went down a treat – they weren't that good so don't worry guys. I'm enjoying the dining hall experience."
Englishman Cheavon Clarke is considered Nyika's strongest challenger but the Kiwi has regularly squared off against him as part of the World Series Boxing league.
"I've sparred with six of the 10 potential opponents in my division so I know exactly what I'm getting myself into. I know I'm leagues ahead of some. You can hope for a draw but all I can do is be me and express myself.
"It's going to be a whole new kettle of fish here at the Commonwealth Games. I'm carrying the weight well and I'm looking forward to putting on a showcase."
Do that, and Nyika may just enjoy a long, dark, strong pint of Guinness.