If you plan to stay in NJ for more than 183-days, I believe NJ will consider you as a resident for tax purposes. EV is exempt from NJ state sales tax. CO has the new EV tax credit on/after July 1, 2023. IRS EV credit, on/after April 18 2023, is based on your modified AGI from the year you take delivery or the year before, whichever is less.
If you now claim you're the resident of CO and get the EV on/after July 1, 2023, you need to pay CO state sales tax, register your EV in CO, get the CO license plate, insure your EV with the out-of-state travel, etc. You get EV credit if you pay taxes in CO.
If you claim you're NJ resident, you pay no NJ state sales tax for EV, get everything done in NJ. As for CO $5K credit for EV, not sure, because you did pay CO tax for 2022 but you become NJ resident and will start to pay NJ state income tax in 2023.
I'm interested to know if the accountant can answer this question for you, too.