She might be re-coloring it because red dye tends to fade easier than other colors. Sometimes it will even start going an orange-ish color.
I like Haruna's and Tomomi's new haircut and color. I think it makes them look a little more mature. Mami looks a little strange to me with blonde hair(because she had very dark hair before). It doesn't look bad though. I wonder if Rina is going to get a haircut...