We visited the Natural History Museum with the children yesterday and in amongst the dinosaur bones, stuffed animals and fossils, I came across this lovely colour chart:
It is thought to belong to the Bauer Brothers (Franz and Ferdinand), travelling botanical artists - even the job title is wonderful. This is one of a series of numbered colour palettes they developed during the 1770's onwards into the early 1800's, for use when they travelled to number their drawings. Later palettes contained up to 1000 drawings.
Examples of their drawings and paintings:
Page from sketchbook for Iris Germanicus showing numerical colour codes as not all of the colours needed could be taken into the field
Grevillea banksii by Ferdinand Bauer (20 January 1760 – 17 March 1826)