You know those neon-colored highlighters people use? The ones that are pink or blue or yellow? Fio has to use hum-drum black ballpoint underlining instead because the bright colors distract her from the underlying print. And she can't use red ink when she is writing out one of her daily lists because it is too bright for her to read on the fly. Yes, Fio's eyes are extremely color-sensitive. Being an artist was not her choice, but her fate.