KGV Australia Shades
Stanley Gibbons defines a Shade (as distinct from a colour) as " variations in the intensity of a colour, or the presence of differing amounts of other colours". In KGV and Kangaroo stamps, shades are significant as they become a marker as to defining the printing of a particular stamp or group of stamps. The particular method of printing meant that the mixing of the ink could vary batch by batch, particularly during the years 1914 - 1920 due to the impact of the first world war upon available materials to manufacture the inks.
One feature to note about the classification of colours is this catalogue is the normal method of ignoring or staying away from names for shades that are subjective, such as watermellon or apple green as such terminology can mean different things to different people, great for selling paint for bathrooms, but hard to deal with if you are trying to classify a particular stamp. Shades are normally defined in basic terms such as green or yellow green. The standard method of compounding colours in the name is to place the predominant colour second. Yellow green is a green that has a yellow tinge to it.
The most common standard used to define the shades in KGV, Kangaroo and other issue Australian stamps is the Australian Commonwealth Specialists' Catalogue. You will find that it generally complies with the above rules, however in certain cases the name relapses to Cypress Green or Terracotta due to historical decisions that were made many years ago and to alter it now would be confusing.
You can purchase a colour key manufactured by Stanley Gibbons that has sample colours for many of the common stamp printing colours. Very useful for trying to tell the difference between a large number stamps of the same colour but different shade.There are many good books that will help you in classifying shades, visit your local Philatelic Supplier.
Refer to the excellent Guides by headbut17 on the KGV 1d Red Shades on Smooth Paper.