>>49623311
I love it too, really enjoyed learning the lore behind it to on one of the episodes of TsunaRaji. Apparently she always wanted to have super cool inner-highlights like that since she was young, she even had multiple attempts during middle/high school where she tried to get it past the teachers by dying it during their class' cultural festival events. Understandably, the teachers always scolded her and forced her to remove the temporary dye quickly though.
She's always been a huge LiSA-fag too, so that's probably why she's so content to stick with the red (apart from Mei.)