Green — there is no doubt about it — is the color of the era. Certainly it has gone through wildly disparate iterations, dating back to the early 1860s when Lincoln issued $450 million in new bills to finance the War Between the States. They were printed in green ink, to distinguish them from other notes, according to one account. Hence the name, greenbacks.

Just over a century later, in 1970, Charles Reich, a law professor at Yale, reversed the meaning of the color with a book that became emblematic of the hippie generation and its aversion to materialism — The Greening of America. To read the copy on the jacket flaps is to capture the early essence of the baby boomers: This book, it said, ” asserts that the many ills of our society…  can all be understood as. . .the usurpation of all values by the modern corporate state…” It offered, instead, a “new vision of human existence — freedom, creativity, humor, love, community. . ..” Wow! Who wouldn’t want all that?

This marked the beginning in America of green as a color of hope, which it long had been in Poland. Or luck, as on the Emerald Isle of Ireland. Or universal love, as in the chakras of India. In the Christian church, green has been the color that adorns the altar during the growing season between Pentecost and Advent.

At the same time, the notion of people being green with envy or inexperience or nausea started to fade in favor of environmental greenery, the healthful habit of green tea, the encouraging signs of green shoots. They all were manifestations of natural order and well-being, standing ever in opposition to the greenhouse effect of gas emissions and other ills ushered in by the wrong-headedness of humankind.  There is no paradox here. Green simply converted to the redemptive side of the ledger, or tried to.

Green has become, also, a sanctuary, as in the Green Zone of Baghdad. In addition, it can loom over contested territory once divided by a Green Line such as the boundary between Iraq and Kurdistan before the American invasion of 2003, a line no longer recognized by Kurds. Another Green Line was drawn — in green ink, like the greenbacks of Abe Lincoln — between Israel and its neighbors after the Israeli-Arab War of 1948. In yet another instance rife with politics, green cards are the ticket for immigrants who want to work in the United States.

Green is the enduring, sacred color of Islam. It also became the banner of Mir Hussein Moussavi who ran against Iranian President Ahmadinejad in June and lost in a landslide that seemed more odd than authentic. Protestors filled the streets of Tehran, wearing green bracelets to suggest, as Moussavi had tried to do, their allegiance to Muslim truth.

Closer to home we have the “mean green” of the University of North Texas, a playful variation on a venerable theme. We have also the elegant green panel at the Meyerson Symphony Center, one of four in a quartet of colors done by Ellsworth Kelly. And no artist can paint green like Ellsworth Kelly.

It all adds up to a color close to nature that has stood for many things in many situations. It is more multi-faceted than some suspect, because of nature herself, which is not always benign. Nature can bring hurricanes, tsunamis, searing summer heat. Taming nature has been a relentless enterprise in the world — sometimes fruitful, often futile. But those who choose to ride the whirlwind of nature, in all its green glory and all its treachery, deserve our attention and respect. Even though it’s a color fraught with paradox after all, still, I’m glad to be living in the age of green.