Coloring hair after chemo?

My mom finished chemotherapy at the end of the summer, and she has about an inch of hair grown back. The hair is very fine, almost fuzzy, and has some gray patches, same as she had before. She wants to color it to cover the gray, but doesn't want to use permanent color. Is there a good semi-permanent hair color that would cover the gray, and not damage her delicate new hair? Thanks!