Some thoughts on color names
There can be no misunderstanding about the color names of the RGB primaries. R is red, G is green and B is blue. Look at these colors and you won't doubt the accuracy of their names.
The CMYK colors may be less obvious. Yellow is exactly that: yellow. But cyan and magenta? Before I got interested in digital color numbering, I only had a vague notion of what exactly cyan and magenta were. Of course I know the colors from the printer cartridges. Cyan I would definitely categorize as "light blue" and not "greenish blue" as it is supposed to be.
And magenta? Ask random persons what color you get when you mix blue and red, and many will say purple. I am convinced that purple is closer to blue than to red, but why and how do I know that? Who determines the exact definition of a color by its name? Who determines what magenta is, and how it differs from let's say violet or pink?
To be honest, I don't know the answer to that question, but I do know how I link colors and color names: by searching on wikipedia. Google "cyan color wiki" and you will find http://en.wikipedia.org/wiki/Cyan which shows you the color and its RGB values. See figure 1. In RGB, it is coded 0,225,255 which puts it right between green and blue. In CMYK it is 100,0,0,0 which... proves our point.
Similarly, magenta is explained on http://en.wikipedia.org/wiki/Magenta, coded 255,0,255 in RGB and 0,100,0,0 in CMYK.
And to finish the triplet, yellow is 255,255,0 in RGB and 0,0,100,0 in CMYK.
What about LAB?
One day, I asked myself the same question about the LAB primaries. LAB has two color channels, covering opposing colors. The A is usually referred to as the green-red or green-magenta axis. I think green-magenta is better because those are really complementary colors. The B is usually called the blue-yellow axis. But are those names accurate? Is the B-negative really blue? Is the A-positive really magenta?
There is an easy test to find out. Start Photoshop and open the Color panel. Switch to LAB sliders and set the L slider to 50, A -60 and B 0. Lightness 50 is not too light and not too dark. And A -60 is not too saturated neither too flat. Those values may be suitable to judge a color.
LAB 50,-60,0 looks like a proper green to me.
Now open the Color Picker by clicking the little square top left in the Color panel. Here we can read out the corresponding RGB values. They are... 0,143,117. So what we thought would be green, is green mixed with a good dose of blue. It is closer to cyan than to green.
Dan Margulis mentions this fact in various places in his books. Sometimes he calls the A negative color "teal". So there we have a name that we can check. Teal, according to wikipedia, has RGB values 0,128,128. It is in fact "dark cyan" and closer to blue than the pure A-negative color.
Figure 2: LAB's A channel
Any way we can search an even better name of the 0,143,117 combination that we found? Well, not easy but it is possible to come close by searching a color group. There is a wiki page for "Shades of Green" (http://en.wikipedia.org/wiki/Shades_of_green) which provides a lot of green variants together with their names and RGB values.
Some of the best candidates I could find were: pine green (1,121,111), pantone green (0,173,131), bottle green (0,106,78) and persian green (0,166,147).
Of course, the same test can be performed for the A-positive values. Convert LAB 50,60,0 to RGB and you will find 206,63,122. Really not red neither magenta but something in-between. Some more searching yielded a lot of candidate color names (really, we have more color names in the red-pink-magenta range than in the green-cyan range!).
I mention a few here: pantone magenta (208,65,126), telemagenta (207,52,118), persian pink (247,127,190), french rose (246,74,138) and china pink (222,111,161).
So what can we conclude from these lists?
First, the green-magenta classification is very inaccurate compared to the RGB definitions of green and magenta. However, green and magenta are a surprisingly precise match with the Pantone color definitions. Both Pantone Green and Pantone Magenta are very close to the A negative and A positive colors. I suspect this is no coincidence. Have the Pantone colors been the basis of the LAB primaries, or the other way round? I don't know, and I don't care.
Point is that naming LAB's A color range "Pantone Green - Pantone Magenta" is not very practical. Too many words. We can better keep the names Green - Magenta with the implicit assumption that we mean the Pantone definitions.
What also strikes me is the Persian Green and Persian Pink that we meet in those lists. Both are pretty good matches too, but they have the same practical drawback that we need two words for each.
But there is another combination that I find interesting, and which goes without the double names. What about: Pine - Pink?
Both are short, four-letter names. Both can go for color names by themselves - we don't have to add "green" or "magenta". And they share three of their four letters. They fit the colors and they fit together.
Pine - Pink. I like that.
What about the B?
On to the B channel. Blue - Yellow. We do the same test as we did for the A channel.
Figure 3: LAB's B channel
LAB 50,0,-60 translates to RGB 0,123,222. So it is blue with a green tint.
LAB 50,0,60 translates to RGB 137,118,0. That is yellow on the orange side. With L as low as 50, it is not light enough to be recognized as yellow, but raise L to 80 and the yellow pops out.
Not many fitting candidates present themselves. Some that I found for the blue were: Azure blue (0,127,255), Brandeis blue (0,112,255) and Sapphire (15,82,186).
The yellow was even more difficult. The color that I found (137,118,0) is too dark to be called yellow or orange, too far away from both green and red, and too light to be called brown. On the wiki page for Shades of Yellow, I found Munsell Yellow (239,204,0), Pantone Yellow (254,223,0), Lemon Yellow (255,244,79) and Gold (255,215,0). All considerably lighter but with a fitting hue.
Some nice combinations can be made.
What about Sapphire - Gold? One gemstone, one precious metal. Not bad.
Or how about Azure - Lemon? Not related except that both have a mediterranean connotation.
There is no clear winner this time, but I found another candidate. The LAB blue is pretty much the color of the midday sky. The associated yellow is not hard to pick: let's call it "sun". Obviously, if the sun has a color at all, it must be white, but a late afternoon sun can easily turn orange-yellow.
So now we have three candidates:
Sapphire - Gold
Azure - Lemon
Sky - Sun
Which do you prefer? Let me know by using the contact page. Thanks!
Gerald Bakker, 19 Feb. 2015
Photoshop by the Numbers