I think it's about her/his hair color, but it can also mean colored pencils, I thought about what is more likely to be and I put color. I was also thinking that instead of "put color" I should write something else, and now I'm waiting for suggestions
Hi MozakStrokavi, lilian canale and maki_sindja! Thanks for your help. I think "put color" means "get suntanned" as maki_sindja said. It is consistent with the picture.