The three primary colours, Red, Yellow and Blue are so called because they are, for practical purposes pure colours. Combining other colour pigments cannot produce them. Although a full range of manufacturer colours are available, some react badly with each other. It is possible to obtain some of nature's colouring by combining any two of the three primary colours.

Three secondary colours are obtained by mixing:

Red and blue to give Purple

Red and yellow to give Orange

Blue and yellow to give Green

Tertiary colours may be obtained by mixing a primary colour with a secondary. All of nature's colours should be obtained by further mixing (in theory, that is) but unfortunately each primary pigment colour has within it very small elements of the other two. When they are combined as a fluid mix they form a grey hue. Hue is another name for colour. Black and White, strictly speaking, are not colours.

To prevent confusion, distinction is made between spectrum and pigment colours. The nature of light rays, that is 'daylight' or the 'light of the sky' are composed of spectrum rainbow colours. These can be formed by raindrops acting as prisms on white light, truly transparent. Understanding the difference between spectrum and pigment colours will help in the representation of skies.

To foil and counter any glaring whiteness on large space areas, for example sky, snow and mist or any blank monotonies which tend to be lacking in lustre, quickly drip on to the damp paper area concerned three primary colours in separate splashes. Apply them in very weak solution taking care not to allow the strength of the red and the blue to dominate the yellow. Blend them together using a little water brushed diagonal strokes over the specified area to give off a beautiful iridescence, an attractive rainbow-like quality. Paintings can never equal the beauty of nature, nevertheless, in the medium of watercolour above all others, some wonderful effects can be achieved.

Although colour distinctions are important only a few hints and suggestions are given. A beginner cannot afford the time, nor is it necessary to go further than elementary knowledge. In any event, many artists use only three or four colours in any one painting. Ask advice at your local at shop, choosing mainly non-staining or relatively transparent staining colours, the latter to be used only for light toned areas.

Experiment and see the results of each colour separately and in combination. Some react badly with one another, for instance, Vermilion (a red) and Ultramarine, (a blue) will produce unwanted black sediment. Yellow and black on the contrary will produce rich greens depending on their ratio. Raw Sienna more transparent than Yellow Ochre and Cerulean Blue becomes chalky when applied in a strong, thick consistency. Prussian Blue and Sap Green stain the fibres of the paper immediately. Thick consistency paint mixture very often tends to muddiness. Put the colours on wet with few exceptions and let the liquid paint do the work. Even if a black area appears on the landscape subject, do not apply neat or diluted black. Mix and experiment with two dark colours to represent blackness. Black paint on paper appears similar to ink spills or black holes in the paper. At all times work within the limits of pigment colours.

This is a specialised mottled effect caused by the settling of some heavy pigment colours into the hollows of textured watercolour paper. After a wash has been laid on a slight slope, rock the board from side to side. Whilst it remains wet it intensifies the granulated 'mottle' effect. When the pigment in the water stops moving, the board and paper should be laid flat and allowed to dry.

Granulation is ideal where large unbroken washes are involved as in a sky or a textured area such as a stucco wall. Two dissimilar colours well chosen of different pigment weight characteristics can give an attractive mottled appearance.

It is a fairly standard practice to combine Cobalt Blue and Light Green, French Ultramarine and Burnt Sienna, also Raw Sienna and Ivory Black to produce this mottle. Depending on the ratio of one colour to the other and brush manipulation, some interesting results will be realised.