Salamualikum sheikh, is it permissible for a sister to buy many different colors hijabs or Abaya that are dark colored? Such as dark purple? Also can they loosen the hijab, or wear a wrap up hijab. Because their ears seem to hurt from wearing it. They are having hard time to practice the hijab.

Don't toy with the hijab. She can try the different Islamic ones that best suit her without reducing the hijab. As for colors, there isn't a specific color, so she wears what is the norm of the country. If it is black then black if it is another color then that color as the ulama have mentioned and Allah knows best.