There is white. There is black. Could there be another?
The NFL officially opened the door for all teams, starting in 2025, to have a third helmet. Teams doing a re-design of their uniforms this season already had the option; everyone can do it next season. The Cardinals already have their regular white helmet and their black alternate helmet, so there is an opportunity to add another.
(Let's get this out of the way -- this news just broke and I have no idea if this is something the Cardinals plan to do.)
There are restrictions. The third helmet has to be worn with one of the team's "optional uniforms," which in the Cardinals' case is the all-blacks. That could be an issue, barring the addition of a Classic (i.e. throwback) or color rush optional uniform, because each alternate helmet has to be tied to a specific uniform and teams cannot mix and match. Nevertheless, it's an option out there going forward.
And to think, I thought we were done with uniform talk for a while.