Okay, so I just noticed this. Nile is wearing a pendant like Erwin but it’s red instead of blue. and this color conflict isn’t the first time we see this. Levi and Erwin also appear in the red and blue color scheme.
I see this a lot in anime and other animation: the Blue vs Red parallels. Some people might think it’s supposed to represent good and evil, but that’s not really the case. Pairs highlighted in red and blue often do appear at odds but are not necessarily enemies. The colors represent duality, both in personality and ideology. The blue is often more calm, logical, and level headed. While the red is more wild, untamed, and emotional.
Red will often act in the moment, not always thinking ahead long term, and the blue will often be more ambitious and plan multiple steps in advance. Despite the differences, Blue and Red often attract and form long lasting friendships or bonds. This is probably because they conflict each other in such a way that they compliment one another. They balance each other.
This is very evident in Erwin’s friendships with both Levi and Nile. Levi tried to kill Erwin when they first meet and Nile held Erwin at gunpoint and opposed him in court because of differing opinions. Despite this, Erwin maintains strong friendships with both Nile and Levi. I think it’s interesting to see that Erwin’s closest friends have been so conflicted with him.