At this time of year my thoughts sometimes turn to the colours that we associate with Christmas: red, green, gold, silver and white, in various combinations. One of the things that I sometimes read about is where Father Christmas always had a red suit or whether he had a green one. I note that in The Lion, the Witch and the Wardrobe, Santa is wearing a dull brownish tunic.
Father Christmas in Narnia
Though apparently according to CS Lewis himself in the book: on the sledge sat a person everyone knew the moment they set eyes on him. He was a huge man in a bright red robe (bright as hollyberries) with a hood that had fur inside it and a great white beard that fell like a foamy waterfall over his chest.
There are also annual stories about whether the traditional red we now associate with Father Christmas was influenced by Coca-Cola for marketing reasons. So, today I thought I would share this blog post about the truth of Father Christmas and red. It does refer to Coca-Cola who, I believe, had a role in popularising our current image of Santa but were not actually responsible for the colour change. This view is also reinforced by this blog post about Santa and red.
Anyway, the thing I read today that inspired me to write this post is actually this blog post which is about colour symbolism and Christmas.
Finally, if you want to explore the meanings that colours have in a more academic perspective here is a link to two papers that are free to read in JAIC – the Journal of the International Colour Association. One was written by me and Seahwa Won (who was my PhD student at the time) and you can see that one here. The other is written by José Luis Caivano and Mabel Amanda Lopéz, well known colour experts in Argentina, and you can see that here.
I am one of the editors of JAIC – the Journal of the International Colour Association. Next year we are planning a special issue of papers about colour theory. One of the good things about JAIC is that it is a journal in which it is free to publish and free to read. So if you want to read some really good colour content please take a look at it here.
However, next year we are having an issue that will collate papers about colour theory. For this special issue we have appointed the renowned colour expert Robert Hirschler as the guest editor. The call for papers is already open (deadline next August) so you can already submit your papers. To do so please click on the link to the special issue where you will find more information.
I just came across an interesting article that suggests that discolouration of the toes could be one of the earliest signs of high cholesterol. High cholesterol – that often results from poor diet (and I should know!) – can lead to fatty deposits on the inside of arteries and this in turn can lead to blocked blood vessels. One of earliest symptoms, however, is a mottled purple colouration in the toes. For more information from the original article please click here.
My colleague at the University of Leeds, Dr Vien Chueng, who is currently President of the International Colour Association (AIC) recently published this article through the University of Leeds on the influence and impact of colour on the way we live. This is part of a series of articles from the University that address our transformational research and collaborations that are helping tackle global challenges and advancing knowledge to create a better future.
I really like this page by John Lovett about colour mixing.
We all know that you can’t mix all colours by starting from three primaries. You can’t do this in theory and you can’t do it in practice. You can’t do it with additive colour mixing and you can’t do it with subtractive mixing. In fact, with subtractive mixing, the oft-cited primaries of red, yellow and blue are actually not a very good choice.
Mixing red and blue pigments, for example, won’t give you a great purple. You will lose saturation and you almost certainly won’t get the vivid purple that is suggested by many colour wheels. However, John Lovett’s page explains how, if you do start with red, yellow and blue, you can do a little better by understanding that there is not just one blue and one red, for example. If you want to mix yellow and blue you should use a greenish yellow and a grreenish blue. On the other hand, if you want to mix blue and red you should use a reddish blue and a bluish red. This reduces the loss in saturation.
However, although Lovett’s advice is superb, you still can’t make all of the colours this way (though you can make all the hues of course). And arguably what Lovett is proposing is a six-primary system rather than a three-primary system. Lovett ends up proposing a six-primary system in an attempt to make the out-dated idea of RYB work.
It’s quite exciting to announce that this week I founded Colour Intelligence with my colleague Dr Kaida Xiao. We have some quite exciting things planned. It’s my second time running a start-up. I formed Colourware Ltd in about 1994 and I only stopped running that company when I became ultra busy at Leeds University in my professorial role and when I was also Head of School of Design. I can’t say any more about what we have planned just now but hopefully I will be able to do that soon.
I received a copy of the book today – A Cultural History of Color in the Modern Age. It is one of a six-book volume published by Bloomsbury. In this one I have a chapter co-authored with Qianqian Pan entitled Technology and Trade. In short, we look at the key technological developments in the 20th century and their effect on culture and commerce. The developments we focus on the growth of the synthetic dye industry, colour imaging technology and colour measurement. You can probably get a copy of my chapter through my ResearchGate page.
You’ll be green with envy if you miss this podcast all about the colour green. Malachite was one of the earliest green pigments and a substantial source was the Great Orme in North Wales (the largest prehistoric mine in the world). Green is also the most dangerous of colours. Scheele’s Green may even have killed Napoleon. The team also discuss the association of green with the devil and with Ireland. The use of colour in movies is also discussed and the use of green in The Wizard of Oz is of particular interest. And did you know that the Statue of Liberty was not always green? You do now. But listen to the podcast for the full story.
Imagine you have a standard (std) and a batch (btx) and you have the CIELAB values of each. How can you analyse these numbers, in particular, the differences? This post explains how to do it.
Let’s start with a real example.
Now what can we say about these two samples. Well, we can calculate the colour difference. If we want to calculate the CIELAB colour difference we can simply calculate the differences in each of the three dimensions, square them, add them and take the square root. Thus DL* = 2, Da* = 10, and Db* = 6. So the CIELAB colour difference is sqrt(4 + 100 + 36) = sqrt(140) = 11.8. This is quite large. Of course, we might prefer to use some other measure of colour difference such as CMC or CIEDE2000. But let’s stick with CIELAB.
The next thing is to look at the individual differences. Since a* is redness we might conclude that the btx is redder than the std (the btx has an a* of 36 whereas for the standard it is only 26). And since b* is yellowness we might conclude that the btx is yellower than the std (the btx has a b* of 9 whereas for the standard it is only 3). However, it is really confusing to look at the data this way. Perceptually, we might be interested in whether there is a chroma difference (is the batch weaker or stronger?) and whether there is a hue difference. Let’s plot these samples in the a*-b* plane of CIELAB.
As you can see, the btx has a larger a* value and a larger b* value than the std. However, we cannot deduce anything about hue or hue differences just by looking at a* or b* on their own. Hue is an angular term in CIELAB space.
As you can see from the above figure, the hue of the standard is 6.6 degrees and the hue of the btx is 14.0 degrees. The CIE method to calculate hue descriptors is to move radially from one sample to another and note which axes we cross. So if we start of with the btx we move clockwise towards the std; we keep going and we cross the red axis and then (if we keep going) we cross the blue axis. So we would conclude that the std is redder (bluer) than the btx. According to CIE guidelines, one of these descriptors makes sense and the other doesn’t.
In this case, I would say that the std is bluer than the btx. In hue terms it doesn’t really make sense to say that the std is redder than the btx when they look quite red anyway. And we would say that the btx is yellower (greener) than the std.
In terms of chroma we calculate the distance from the centre for each of the colours. As you can see from the diagrams, the batch is much further out from the centre than the std.
So, in conclusion, we would say that the btx is lighter, stronger and yellower than the std. The std is darker, weaker and bluer than the btx.
The point of this is to highlight that we cannot make decisions about hue and chroma by looking at just a* and b*. We need to look at both a* and b*. Better than trying to do this is to calculate the polar coordinates, hue and chroma. These are generally more helpful than the cartesian coordinates, a* and b*. In my experience, people have a reluctance to think in terms of polar coordinates and I think this is because they have much greater experience at school with cartesian coordinates. Everyone spends their schooldays looking at certesian plots of x vs. y don’t they? But getting to grips with polar coordinates in colour science will really pay off in the long run.
Notice that just because the batch has a larger a* value than the std, this does not make the batch redder. In fact, as can be seen from the first diagram, it is the std that is closer to the a* (red) axis than the btx, despite having a smaller a* value.
The Over The Rainbow team discuss the colour yellow. Yellow Ochre was one of the earliest pigments used by mankind. Orpiment was also widely used in antiquity despite it being based on arsenic and being poisonous. Yellow has also long been an important colour culturally. The Greeks – starting from Empedocles – believed that the world considered of four elements; each of the elements was associated with a colour. Yellow (or a yellow-green colour) was associated with earth; white with air, black with water and red with fire. This tetradic thinking about 4 special colours continued until the 14th or 15th Century; the idea of three special colours is a relatively recent idea. Yellow is probably the least favourite colour and invokes quite different reactions in different people. It is, perhaps, the marmite of colours.
