The Vietnamese word "khởi sắc" means to prosper or to thrive. It is often used to describe a situation, business, or even a person's life improving or becoming more successful.
While "khởi sắc" primarily means to prosper or thrive, it can also imply a positive change or an uplifting situation. For example, you might say someone's mood has "khởi sắc" when they become happier.