Do you like Joni Mitchell? I love Joni Mitchell. When I was little my mom used to sing this one song to me, "Little Green," which is about the child Joni gave up for adoption when she was 22. It's the saddest song in the world and I absolutely loved it. My mom is great. Happy belated mother's day, love you Mama!

The song is on Joni's fourth album, entitled "Blue." The album also features the song "Blue," which has to be one of my least favorite Joni Mitchell songs. The lyrics start out "Blue songs are like tattoos / You know I've been to sea before / Crown and anchor me / Or let me sail away." I mean come on Joni, you're better than that.

But as dumb as those particular lines are, we sort of know what she means. It has something to do with tattoos that sailors would get or with loving someone who won't take you or leave you or possibly about Joni's failed career in the Merchant Marines.

But why do we understand so clearly what she means by "blue?" Blue has all these intense cultural associations - you can feel blue, sing the blues, you dress a baby boy in blue, blue bloods are the elite, the Virgin Mary wears blue and there is a particular shade called Aggie Blue and no one seems able to explain what makes it special or even what it is.

Hey, since we were talking about "Little Green" earlier, did you know that some languages don't have separate words for green and blue? Tswana, Vietnamese and the Lakota Sioux language use the same word for both colors. In all three you sort of have to guess the shade based on context.

Anyway, why do we put so much emphasis on blue in the first place? Well, there's the sky for starters. It's above us, and it sure does look blue. I say "look" blue because as we all know the sky is in fact every color but blue. The atmospheric particles absorb light of longer wavelengths reddish/yellowish light - but scatter the blue/green/violet end of the spectrum.

Then there's water. I hear you out there, fellow humanities majors, being all sassy and telling me that bodies of water are just blue because they reflect the sky. Um, first of all, don't sass me, and second of all WRONG! Because science says that while water may appear colorless in small quantities, it actually has a slight blue tint.

So blue is all around us, and it makes sense that we would be interested in it. But that doesn't explain why we give it the meanings we do. I mean, why is sadness blue? Real talk? I don't know. The first association of the color and the feeling in print is from Chaucer's "Complaint of Mars" from 1385. So it's real old. The internet seems to think it goes back to the phrase "to have the blue devils," (i.e. to be depressed.) But the origins of that phrase seem to be lost to us.

The other associations are easier to explain and I'm gonna do it really fast. Before 1900, kids wore neutral colors and styles. Then in the 1900s, blue was the color used to dress little girls because it was seen as delicate and contemplative and boys wore pink because it's a more childlike version of testosterone laden red. Then suddenly in the '4os, manufacturers decided to market just the opposite pairings and American parents were like, "Oh no, we've been turning our little boys into perverts and we didn't even know!" So we all made the switch.

We call rich people "blue bloods" because in the old-timey Europe they stayed inside all day and didn't have to work in the fields, so their pale skin showed their veins, which appear blue through some skin colors.

The Virgin Mary wears blue because Byzantine royalty wore blue, and the Byzantines were some of the first people to make Christian art, so they basically painted her as a queen. Also in Medieval times, lapis lazuli was the most expensive gem around, so making paint out of it to depict Mary showed that you really, really liked Jesus, or at least that your wealthy patron did.

I can't help you with the Aggie Blue thing. Some things in life are meant to remain mysteries.