Interesting article in NY Times about the toxic side of green, both as a movement and the color. No mention of indigo in the article, but does mention how so many of the older greens faded to blue. Below is a quote from the article.
Even if they succeeded, the results often faded or discolored, as did green dyes. When the 19th-century British designer William Morris created wallpapers inspired by medieval tapestries, he copied the blue hues in the originals. But most of those “blues” were really greens, which had changed color over the years.