I would have had these stand in as Hand Ninjas. But now I have enough of those, so I'd probably buy one and consider it a unique character. Then I'd get one of each color they make available and they can become pilots of giant animal robots.
I'm meh on the rainbow ninja army builders, but I want them for everyone who's about them- might bite if they include the man catcher, those things are gnarly.
Also, Sigma Six was kinda nuts, huh? Like full time wackadoo.
I'm going to be surprising, maybe, on this one and say no, I don't need red ninja. Ninja-Ku covers the classic 'black pajamas' ninja for my collection. I have no attachment to the idea of generic red ninjas (in fact, I kind of hate it). And if I wanted a Cobra-specific generic ninja, I want it to be Ninja Viper. Which is not red.