The virtues of making your own colour charts
Why should you bother making your own colour charts and mixing charts? Why not just use the ones supplied by the manufacturer?
Anyone who's visited my studio will see the walls covered in colour swatch charts of different media (see an example of some of them in Fig. 1). In fact, whenever I start a new medium, or a new brand within a medium, or a new style of application within a medium, I draw up a colour chart for it. Despite whether I have a perfectly good colour chart supplied by the manufacturer or not. Why bother?
There are several reasons I do this (aside from the fact I'm a chronic list-builder):
Most importantly, raw pigments are never the same as printed colours in manufacturer catalogues, or indeed the paint used to dip the end of the pencils, or the paint seen through the semi-transparent tube, or pastel sticks covered in pigment dust. Choice of colours is crucial to the artistic process, particularly for art that aims for realism or semi-realism - you want to give yourself the best possible chance of choosing the right colour, by choosing based on what the pigment actually looks like on the ground (canvas, paper, etc) of your choice.
Manufacturer colour ranges change over time as new pigments are added and older less popular pigments are taken out of production. You may have tubes from an earlier catalogue that are no longer displayed in the current catalogue (which doesn't necessarily mean that the colours aren't any good anymore).
Basic pigment colour charts allow me to test some of the intrinsic properties of the different pigments within a brand's colour range.
When testing watercolour pencils, for instance, the appearance of the 'dry' pencil pigment can vary considerably from the 'wet' pigment (ie, when a brush with water has been applied). Although most of my watercolour pencil work takes advantage of the 'wet' properties of these pigments, the pencils provide interesting properties for texture when used without water, or used dry over already dried previous washes. For this reason, when making a colour chart with watercolour pencils, I leave one corner of the coloured swatch for each pigment dry (see the chart second from the top on the right of Fig. 1).
Tube paints (such as acrylics and watercolours; see bottom left two colour charts in Fig. 1) can readily provide a variety of tints for each pigment (from pure pigment through to diluted pigments; either mixed with water or acrylic painting medium), and it is helpful to have examples of these tints when choosing colours. Some pigments and tints behave in unexpected ways - some are so dark that they appear almost black right through until they are > 50% diluted, when their hue becomes apparent. Some pigments never appear this dark even applied as pure pigment. You can visualise this range of tints simply by diluting your pigments from pure pigment in one corner to almost no pigment in the opposite diagonal corner in each swatch of your colour charts.
Tube pigments also tend to differ individually in their transparency when mixed with water or another medium (such as clear painting medium). Manufacturers usually provide a guide to transparency (and lightfastness) in their catalogues, but oftentimes I have found these guides to be very rough, and my pigments behave somewhat differently. You can test transparency with your colour charts by drawing a diagonal line in pencil through each colour swatch (from the pure pigment corner to the diluted pigment corner) before applying the paint (see for example the bottom right image of watercolours in Fig. 1). With transparent pigments you can see the pencil line through the paint along its length, but with semi-transparent or opaque pigments, your pencil line might disappear at a variable length along the pencil line towards the pure pigment end.
Especially with mediums designed to be mixed in a palette (for example, watercolours and acrylics), it can be helpful to create colour mix charts in addition to the basic raw pigment colour chart. An example of a green colour mix chart for my Winsor & Newton artists watercolour paints can be seen in the bottom right of Fig. 1. Artists painting with watercolours generally make good use of the properties of the split primary colour wheel (I'll leave describing this for another post), and they mix most of their colours from primary colours. This means that secondary colours such as greens are mixed from yellows and blues. Although the manufacturers typically produce a small range of these secondary colours as raw pigments in tubes, the range is generally never so good as those you can generate by mixing. Interestingly, not all combinations of yellow and blue make 'good' greens (the principles of which are covered when you understand the colour wheel), and by constructing a colour mixing chart, you can immediately find the mix of pigments that produces the colour you're after. To make the chart in the bottom right of Fig. 1, I listed the raw blue pigments down the page, and the raw yellow pigments across the top, then proceeded to mix the respective colours in the grid.
So there you go. Good colour charts and colour mixing charts are easy to make, and always helpful to have on hand when choosing your paints. If you have recently invested in a new set of paints, pencils or pastel sticks, they also get you right into using the colours, even when you're initially feeling a bit tentative about opening the brand new tubes etc. I recommend all art students start out by constructing a colour chart of sorts.