Why did you draw Anzu wearing the Kimisaki 3rd year uniform when she transferred to Yumenosaki as a second year?
I'm not the best source for EnGirls facts so I might be missing any important info or statements, but I do have a short and long answer for that actually :DD
Short answer is, well that's because Anzu is supposed to be wearing a green uniform!
In Paradise, the event that takes place during Anzu and the rest of the Troublemakers' first year, before she transfers, they are all wearing the green uniform:
The long answer is, just like Yumenosaki, Kimisaki does do the red=1st year blue=second year green=third year color distinction too, but it's notable that the arrangement might have been discarded/ignored eventually for convenience once the stories start showing events from past and future, and the distinction specified applies to the specific time period of the game. I forgot where this was stated, like if it was an art book or a question answered by the EG account since I was just told this at one point, but apparently Kimisaki's uniform doesn't circle between the three colors when you study there, but you're gonna be using the same color as a batch until you graduate because it's less costly that way (which makes sense, changing your entire top every year seems more inconvenient than changing a tie).
I've wondered the same thing as you at one point, but realized without knowing that, it can also be observed in some of the events that happen in the past and future; where the girls still wear the same color they do then as they do in the main timeline of the game's story
Paradise and Grimoire are an examples of events from the past, where third year students, who need to be shown as their first year selves prior to the start of the game, wore their green uniform you would see them in during the events of the main story.
In the final main story event, which takes place during the now president transfer student's third year in highschool, everyone is still wearing their colors from the previous year/main story timeframe (Natsumi wears blue, Ruka and Shizuku wears read, etc.) (It's def not because everyone is supposed to be roleplaying as their selves from a year ago for the big reunion that's unrelated TwT)
In Full Voice, where Suzu visits and joins the radio program as a guest Alumni, everyone is wearing their usual uniform colors too.
So it can be observed that yes, the colors of the kimisaki uniform doesn't rotate and that they only wear whatever color they came in with. Hope that helps :DD If I missed any important details or fun facts, feel free to give me a heads up! I love learning more about engirls :))
