Tag Archives: colorant

what colour is indigo?

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Seems to be a lot of people typing

what colour is indigo

into google. Why all the fuss about indigo?

In case you are one of those people I can tell you that in the spectrum indigo was generally considered to be associated with wavelengths in the range 420nm – 450nm though many would argue that it is not in the spectrum at all and that light below about 450nm is considered to be violet. Have a look at my earlier post about why indigo is generally not considered to be in the spectrum by modern colour scientists.

In terms of RGB (sRGB for the techies) it can be approximated as R=75, G=0, B=130 and this looks like this:

Though of course, the RGB on-screen representation is not the same colour as the indigo in the colour spectrum since every colour in the spectrum is outside the gamut of your RGB display and therefore cannot be properly shown.

The word indigo is named after the blue colorant obtained from plant indigofera tinctoria.

feeling blue?

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In the 1800s a family in eastern Kentucky started producing children who were blue. In was apparently the result of a recessive gene and in-family breeding. The family lived an isolated life and there was little opportunity to mix with others. Medically, the condition is called methaemoglobinaemia – the ability to carry oxygen in the blood is reduced resulting in it being a darker colour. As eastern Kentucky became more populated there were fewer children born with the condition though the gene still exists today. See here for more details and the original story.

This is not perhaps the only case of blue people. The picts in Scotland were known as blue people. They fought naked with their bodies painted with woad – a blue colorant. And there is also the Ainu, people indigenous to Japan whose skin was often described as blue. Some people believe there was an ancient human race – the blue moovians – who lived about 60,000 years ago. But I think this might be new-age clap-trap.

Of course, talking of blue people we should mention Avatar. This is a movie that has a lot of hype and I had no interest in seeing it. I didn’t see it for a while but then I thought I should see what it was like. Generally, I thought it was great even if the militaristic movements at the end were a bit over the top. Some people have argued that the movie is racist – that blue is the new black. Apparently, all the humans in the movie are played by white actors and all the blue Na’vi by non-whites; and the blue Na’vi have been said to represent the native Americans in their use of bows and arrows. Worth reading.