Hookers Green is a modern version of a colour originally invented by William Hooker who was a botanical illustrator working for the Royal Horticultural Society who needed a dark green colour for painting the many dark green leaves he had to paint. This was in the early years of the 19th century. He found that a mixture of Prussian Blue and gamboge which was a pigment made from the bark of a tree from Cambodia, make the exact sort of dark rich green that he needed. Gamboge was very similar to the modern Aureolin but unfortunately it was very fugitive. in the period around the beginning of the 19th century Hooker was very well known in London and his illustrations greatly admired and so many other artists saw and wanted some of his dark green colour and it wasn???t long before all colourmen were making Hookers Green watercolours. John Sell Cotman, the watercolourist, helped popularise the colour. His Greta Bridge painting of 1805 made extensive use of it. The colour did appear in some oil paint ranges but it was as a watercolour that it was most popular during the 19th century because so many landscape artists of the day were using watercolours and the colour was especially useful for landscape painters.
The permanency issue was a problem, though. At first a substitute was developed by replacing the gamboge with Cadmium Yellow Medium but it didn???t have the olive quality of the original. Eventually a coal tar dye was developed with a suitable colour that resembled the mixture with gamboge and there was initial belief that it was permanent. That proved to be illusory and when ASTM testing became widespread at the end of the 20th century many artists discovered to their horror just how impermanent it proved to be. Since then various modern and genuinely permanent mixtures have been developed to match the Hookers Green shade. Some artists prefer to make it themselves by mixing Phthalo Blue with Aureolin or Yellow Oxide but most prefer the more accurate mix available in the tube.
It is when using Hookers Green on the palette that it is easy to understand why this colour remains popular after so long. Dark greens or found everywhere in nature but they tend to be the sort of olive types of green like this. Hookers Green has only two real uses - making greens that you are likely to see in nature and as a darkener for other greens. It is always better to darken a colour by using a related but darker colour rather than black which would drain the colour out of the resulting mixture. Only recommended where draining the colour is what is needed.
Making natural greens is very easy. Mix Hookers Green with Australian Yellow Green for a very rich range of forest greens suitable for rainforest and verdant landscapes. An earthier sort of green comes from using Iso Yellow for the mixture and Yellow Oxide or Raw Sienna make mixtures that are earthier again. A quite different green comes from using a light lemon yellow such as Nickel Titanate and a greyed gum tree sort of greyish green is created by the mixing of Hookers Green with Naples Yellow Light. Both John Sell Cotman and William Hooker would be very envious of the many excellent yellows the modern artist has to mix with Hookers green but they would also both be very pleased that the colour that they loved so much continues to be an artists favourite.