This is Scientific American 62nd Science. I'm Cynthia Graber.

Many people remember the colors of the rainbow by the acronym Roy G Biv for red, orange, yellow, green, blue, indigo and violet.

Well, the color indigo just made news.

Indigo gets its name from the plant indigo Ferretinktoria and its relatives,

which supply the dye that makes fabric the rich beautiful color between blue and

violet.

Indigo dye was used around the ancient world in fabrics created from Egypt to China to

Meso and South America, and it's in South America that researchers recently found the oldest

known example of fabrics dyed with indigo.

The artifacts were discovered at Waka Prieta, a ceremonial mound on the coast in northern

Peru, but their color was initially hidden by the gray tones that had leached into them from the materials used in the mound itself.

But when a conservator carefully washed the fabric, the true colors reappeared.

And it was at that point that I realized we had probably had indigo

and it was probably the world's oldest indigo.

Jeffrey Splitster, an anthropologist at George Washington University.

Which was really exciting.

I hadn't thought I'd be discovering, or we would be discovering the world's oldest indigo

when I took on this project.

The research is in the journal Science Advances. The dyed fabric is about 6,000 years old.

In the Middle East there are inscriptions that discuss blue fabrics that date to about 3,100 BC.

These are just texts though.

And so we think they're referring probably

...