The Palette/green/Made in a lab or a works
Phthalo green
Phthalo blue with chlorine bolted on: the strongest, darkest, coldest green available, and the one every painter warns beginners about.
Also called phthalocyanine green · Monastral green · Winsor green
- Hex
- #123524
- RGB
- 18, 53, 36
- Pigment index
- PG7
- First used
- 1938
- From
- Britain and Germany
What it is
Chlorinated copper phthalocyanine. Swap some chlorine for bromine and it shifts yellower, which is PG36.
How it is made
Copper phthalocyanine (the blue) is chlorinated, which shifts its absorption and turns it green. Up to fifteen or sixteen chlorine atoms go onto the molecule. The bromo-chloro version is a brighter, more yellow-green, and between the two the range covers most of what industry needs.
Like the blue, it is cheap, completely lightfast, chemically inert and absurdly strong. It is the default green of the modern manufactured world.
Phthalo green, Chemical compound. Wikipedia's description, not ours.
The history
This and phthalo blue between them replaced almost every other green and blue in industrial use within about twenty years. Green plastic, green ink, green paint, green fabric, mostly this molecule.
In painting it has a reputation problem and it is deserved. A phthalo green out of the tube is so dark and so saturated that it looks nearly black and reads as artificial in anything representational. Used at one part in twenty with an earth colour it is superb; used straight it ruins pictures, and generations of teachers have told students to leave it alone rather than explaining the ratio.
It also makes the best blacks. Phthalo green mixed with a deep red (alizarin or quinacridone) gives a chromatic black with more depth than any black pigment, because the eye keeps finding colour in it. Almost every painter who claims not to use black is using this pair instead.
Where it is used
Printing ink, plastics, coatings, textiles and artists' paint. If a green object near you is not a plant, it is probably this.
Its relevance to a designer is the same as phthalo blue's: the green a screen shows and the green a press can print diverge because the press is working with this actual molecule. The bright acid greens that look extraordinary on a display are outside CMYK, and a brand built on one will need a spot ink or will look different everywhere it lands.
Go and look at it
Any green printed on a press
Packaging, magazines, signage
Look at the halftone under a loupe: green is made of cyan and yellow dots, and the cyan is a phthalocyanine.
How it behaves
- Made of
- Chlorinated copper phthalocyanine. Swap some chlorine for bromine and it shifts yellower, which is PG36.
- Opacity
- Transparent. It stains rather than covers, so it can be glazed over another colour.
- Lightfastness
- Permanent. It will outlive the thing it is painted on.
- Extreme tinting strength. Start with a tenth of what looks reasonable.
- Mixed with a transparent red it gives a better black than black.
- Two common variants: PG7 blue-shade, PG36 yellow-shade. They are not interchangeable.
The numbers
All derived from the hex, never typed beside it
- HEX
- #123524
- What a browser and a design file want.
- RGB
- 18, 53, 36
- The same three numbers in base ten. Light, not ink.
- HSL
- 151°, 49%, 14%
- Hue, saturation, lightness, how a person describes a colour.
- CMYK
- 66, 0, 32, 79
- Arithmetic only. A real separation depends on the press, the paper and a profile.
- LAB
- 19, -18, 7
- Perceptual. L* of 19 is how light this actually looks, which HSL gets wrong.
This hex is an approximation, and a page about pigment has to say so. Phthalo green is a substance. A ground mineral scatters light from thousands of separate grains at slightly different angles, and no single sRGB value is that event. It is a flat average of a photograph of it, and the real thing is outside what a screen can emit. Use the number to specify a screen colour. Do not use it to judge the pigment.
Where it sits on the wheel
Hue 151°
Its opposite, by the diagram
The arithmetic opposite, 180° round in HSL. Useful, and not the same as the opposite a painter mixing pigment would name, that wheel was built for paint.
Lighter and darker
Towards white
Mixing with white does not only lighten, it dulls and cools. This is why a pale tint of a brand colour so often looks chalky, and why a designed light shade beats a generated one.
Towards black
Mixing with black kills the hue as it darkens. A better dark is usually the colour plus its neighbour round the wheel, which is what every painter does instead.
Can you set type on it
Handgloves
White on it
13.46:1 · AAA
Handgloves
Black on it
1.56:1 · Fails
Handgloves
It on paper
12.77:1 · AAA
Handgloves
It on ink
1.36:1 · Fails
4.5:1 is the floor for body text and 3:1 for large text, by WCAG. Treat it as a minimum you may not go under rather than as a target: plenty of pairs pass at 4.6:1 and are still unpleasant to read for a page, and the checker will not tell you that.
Read more, elsewhere
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