Now, it's time for Words and Their Stories -- our weekly program about common, everyday expressions in American English.Usually, we talk about words and phrases that Americans use without even thinking much about them.But, of course, anybody can make up a phrase and give it meaning.By the way, there's actually a phrase for this act: to coin a phrase means to invent a new saying.The Grammarist website explains that using the word "coin" as a verb began in the 1300s.It related to putting an image on a piece of metal money.But the expression did not come about until 500 years later, when some English speaker coined the phrase "to coin a phrase."Anyway, today we begin with a phrase that scientist Wallace Nichols coined in more recent years.It explains how people feel when they are near water.That phrase is "blue mind."It is also the name of Wallace's book, published in 2014.He uses the phrase to mean a sense of calm and happiness one has near a lake, river, ocean or other body of water.In this phrase, the color blue is positive.It suggests both the color of water and a feeling of mental quiet.The color blue is also sometimes linked to a feeling of security, say researchers who study how colors make people feel.If you call someone true blue, you mean you can depend on her completely.A true blue friend is loyal and trustworthy.A friend like that is extremely valuable.You might even say that someone who is true blue is worth her weight in gold.But that would be mixing idioms!In some phrases, blue relates to being the best.If you win top prize, you win a blue ribbon.Sometimes you really do get a piece of fabric that is the color blue.But you can also just describe something that is excellent with the adjective "blue ribbon" – such as a "blue ribbon restaurant."In business, a successful company that has a very positive public image can be called a blue chip operation.If you own a piece of that company, then you own blue chip stock. Anything that is of high quality can be blue chip.A writer on the business website Motley Fool reports that English speakers started using the term in the early 1900s.It relates to the game of poker. In the game, people use flat, round pieces called chips.The blue chips had the highest value.At the end of the game, players exchanged their chips for real money.So it is no surprise that the more blue chips you gain, the better!But in some other English expressions, the word "blue" is linked to some more complex ideas.If you have the blues, you are sad, even depressed.The website Word Histories says that this sorrowful meaning appeared in a story in England in the 1400s.The color blue related to skin that was hurt or bruised.Artists may also go through a blue period.This is a time when their work suggests painful feelings.Hopefully, those low times do not come very often – perhaps once in a blue moon.This expression has come to mean happening rarely.It refers to the unusual times when one month includes two full moons.The second moon is a "blue moon."Such an event is seen as special and noteworthy.In comparison, something that is a bolt from the blue is unexpected and usually bad.Let's say you and your business partner had just launched a new store.You thought you were working well together.So, the news that she was leaving to take a new job was a bolt from the blue.The idea is that of lightening or thunder appearing in a cloudless sky.News of unexpected illness or a sudden death can also be a bolt from the blue.So, what does the color blue mean for you?Calmness, loyalty, sadness, surprise or something else?After all, every culture and every person reacts to colors differently.Here's a fun challenge for you: Coin your own phrase with the color blue and send it to us in the comments section.Until next time, this is Words and Their Stories.