We let Carus color her hair and she decided on doing a sunset look - orange with red on the ends. We didn't want to bleach her hair since bleaching is so damaging, so it was just coloring over her natural color; not quite as bright result though. I still freaking love it!
We mixed Manic Panic colors Electric Banana and Electric Lava for the orange, and just used the Electric Lava for the ends. We are considering going over the orange with an orange color like Tiger Lily, but haven't fully decided yet. Manic Panic are semi-permanent and vegan. I swear her hair feels softer post coloring and it doesn't smell awful either. It took me about an hour to get the color into her hair because I'm slow and wanted to be sure I got her hair covered and then we left it on for an hour before we had to wash out because of bedtime. You can leave the dye on overnight if you want, but we didn't want to risk a mess. The color will fade/washout fairly quickly, especially if she uses a stripping shampoo or hot water to wash her hair, but should last a month or two.
She wants to do a blue or purple next - or maybe a pink. She hasn't decided yet.