Nah keep the colour scheme simple and just go black and white.
• Nobody in the NRL is using the black and white scheme, so the team can corner the market.
• It's inoffensive. So much so that normies would happily wear it in their day-to-day lives without the fear of standing out.
• It synergises with the mascot perfectly.
• It's super easy to create great jerseys and integrate sponsors with a black and white scheme.
It ticks all the boxes without the need to throw in teal or the traditional Canterbury red into a league that's already oversaturated with blue and red schemes.
As an alternative they could achieve the same outcome with black, white, and silver if they want something a bit more extravagant than just black and white, but you've got to be super sparing with silver or it looks crap.
The Raiders are the only team I've seen pull black and silver off really well, but they basically wear black t-shirts and restrict the silver to their helmets, pants, and namesets, which an NRL side couldn't copy for obvious reasons.
Then again, silver shoulder or arm bands, collars and cuffs, and other super simple and traditional designs like that would result in some of the nicest jerseys in the NRL, if they integrate the sponsors well.
If they simply must add another colour to the scheme then maybe a sea green, but there's no need.