Honestly I hear some that have problems and I think it's because they are coloring on freshly washed hair, and not applying Vaseline around the hairline. Some aren't doing spot testing first either. So here are my tips for hair coloring.
1. don't wash your hair for one to two days before coloring. (that way your natural oils can help protect your scalp)
2. To prevent staining around your hairline put your hair up in a pony tail and apply a thin layer of Vaseline all around and on your ears before starting.
3. Test before trying a new product. You maybe sensitive to it.
4. Start with the minimum time then work your way up to a longer time. (my hair dresser always ends up going waaaaay longer than the maximum time even for her stuff so I know 45minutes at the least for me. My SIL just barely the minimum time.)
5. Lock the kids out when doing your hair. (trust me on that one!)