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I took the time to go through and solve the quiz. 6 different colours are used to highlight certain lyrics during the live, which when put into the order of the coloured Joshu-kuns read out "あなたの大好きなひとがこの世界でスタートした日", or "The day your favourite person started in this world."
Which is how you get the password of Koyori's debut date, 20211128. At least I'm guessing that's the password, since I can't get past the "Too Many Attempts" to check it.