"In the pink" is an English idiom used to describe someone who is in the absolute best possible physical condition. People often use this phrase to describe someone who is in peak condition without any significant ailments worth mentioning. This phrase is often used to as a way to contrast someone who is not feeling well or has a variety of maladies. While the origin of "in the pink" as an indicator of health is hard to ascertain, the phrase can be traced back from when it was used to describe anything that was the best example of a particular group.
It is not uncommon for people who speak English to take advantage of certain colorful words and phrases that may not mean what their literal definitions might indicate. These words or phrases, also known as idioms, tend to gain their accepted meanings from the way they are used in the culture, as opposed to their literal interpretations. Such phrases are especially useful in lending impact and expressiveness to speech. One popular idiom that has been used for hundreds of years is the phrase "in the pink."
If someone is described with this idiomatic expression, he or she must be in very good health. This phrase is used as an extreme, meaning that a person described in this matter is far above average in health and fitness. Instead, those people who merit this phrase have to be in exemplary condition compared to others. As an example, consider the sentence, "I just got a checkup and I received a clean bill of health, so you could say that I'm in the pink."
Many people often use this phrase to contrast another condition whereby a person is not healthy at all. They can do this by comparing a person's health at different stages of their life, or they can compare one person to another. For example, someone might say, "It's a shame how she went from being completely in the pink to having so many health issues just a few years later."
The phrase "in the pink" has been used for hundreds of years going all the way back to playwright William Shakespeare in the 16th century. For most of that time though, the phrase did not refer specifically to health. Instead, it was used to describe anything that was the best of a specific batch of things. It was only in the 20th Century that it gained its association with health.