Editing Indigo (section)

===1800s===
In 1821, [[Abraham Werner]] published ''Werner's Nomenclature of Colours'', where indigo, called ''indigo blue'', is classified as a blue hue, and not listed among the violet hues.  He writes that the color is composed of "[[Prussian blue|Berlin blue]], a little black, and a small portion of apple green," and indicating it is the color of blue [[copper ore]], with Berlin blue being described as the color of a [[blue jay]]'s wing, a [[hepatica]] flower, or a blue [[sapphire]].<ref name="Werner">{{cite book |last1=Werner |first1=Abraham |title=Werner's Nomenclature of Colours |date=1821 |location=London |page=41 |url=https://archive.org/details/gri_c00033125012743312/page/n41/mode/2up|access-date=30 October 2023}}</ref>

According to an article, ''Definition of the Color Indigo'' published in ''[[Nature (journal)|Nature]]'' magazine in the late 1800s, Newton's use of the term "indigo" referred to a spectral color between blue and violet. However, the article states that Wilhelm von Bezold, in his treatise on color, disagreed with Newton's use of the term, on the basis that the pigment indigo  was a darker hue than the spectral color; and furthermore, Professor [[Ogden Rood]] points out that indigo pigment corresponds to the cyan-blue region of the spectrum, lying between blue and green, although darker in hue. Rood considers that artificial [[ultramarine]] pigment is closer to the point of the spectrum described as "indigo", and proposed renaming that spectral point as "ultramarine". The article goes on to state that comparison of the pigments, both dry and wet, with Maxwell's discs and with the spectrum, that indigo is almost identical to [[Prussian blue]], stating that it "certainly does not lie on the violet side of 'blue.'" When scraped, a lump of indigo pigment appears more violet, and if powdered or dissolved, becomes greenish.<ref name="Nature">{{cite journal |title=Definition of the Color Indigo |journal=Littel's Living Age |date=1880 |volume=145 |issue=1869 |url=https://en.wikisource.org/wiki/Littell%27s_Living_Age/Volume_145/Issue_1869/Definition_of_the_Color_Indigo |access-date=30 October 2023 |quote=Newton denoted by the name of "indigo" the tint of the spectrum lying between "blue" and "violet." Von Bezold, in his work on color, rejects the term, justifying his objection by observing that the pigment indigo is a much darker hue than the spectrum tint. Prof. O. N. Rood, who follows Von Bezold in rejecting the term, brings forward the further objection that the tint of the pigment indigo more nearly corresponds in hue (though it is darker) with the cyan-blue region lying between green and blue. By comparing the tints of indigo pigment, both dry and wet, with the spectrum, and by means of Maxwell's disks, it appears that the hue of indigo is almost identical with that of Prussian blue, and certainly does not lie on the violet side of "blue." Indigo in the dry lump, if scraped, has, however, a more violet tint; but if fractured or powdered, or dissolved, its tint is distinctly greenish. Prof. Rood considers that artificial ultramarine corresponds much more nearly to the true tint of the spectrum at the point usually termed "indigo," and he therefore proposes to substitute the term "ultramarine" in its place, the color of the artificial pigment being thereby intended. |archive-date=30 October 2023 |archive-url=https://web.archive.org/web/20231030033534/https://en.wikisource.org/wiki/Littell%27s_Living_Age/Volume_145/Issue_1869/Definition_of_the_Color_Indigo |url-status=live }}</ref>