in the pink指的是一个人非常健康、精力充沛、容光焕发、满面红光。我们知道，健康的人往往气色红润，这大概就是这个短语的来源吧。

【例句】
The children all looked in the pink after their holiday.
孩子度假后个个容光焕发。

People sometimes say you are in the pink when they are in good health.
当你健康状况很好的时候人们有时会说你看起来红光满面的。