Colour Theory and Palette Organisation
The images and notes below are from a course I taught in Brisbane, Australia that offers theoretical instruction and practical exercises in:
Basic principles of colour theory including colour relativity, explanation of Hue, Value and Chroma, Coloured lighting and local colour
Colour mixing in oil paint
What is a colour gamut and reasons why you might want to limit the range of colour for a picture
Colour design in relation to pictorial composition - in particular harmony and contrast, dominant and subordinate colours, and discords, and tonal design in relation to colour design
Click to enlarge the diagrams and view captions
Palette organisation using a colour gamut from a triad of relative primaries (In this case Yellow Ocre, Cobalt Blue and Permanent Alizarin Crimson), with mixed secondaries and tints of each Relative Primary and Secondary. This provides the 12 colour set of colours at top left for easy colour adjustment. At the bottom a string of colours has been mixed with palette knife and then free mixed with brush.
A colour wheel showing the relative hue and chroma of various tube colours. The back ground grey circle has been matched to a digital photography grey card to give a true mid tone neutral at exactly half way between black and white. There is an overlay of plastic showing a colour gamut of the same triad as the diagram at left. the colours between these relative primaries have been mixed and resulted in a triangular shape. The square at top right is an estimation of a relative neutral for this particular triad - that is to say a colour that is located an equal distance from all the primaries.
This diagram is from the Munsell.com website and is a nice representation of the idea of three-dimensional colourspace, in which hue, value and chroma are organised as a 3D volume. Value/tone is on the vertical axis, while Hue and Chroma are distributed as usual around the circle of the horizontal axes, with zero chroma (or a perfect grey) at the centre.
Diagram 4: Same light, varied chroma of objects
In each of the three images, the light is the same, but the chroma of the strips is reducing from the top image top to bottom image
The five right most strips in this image are a five tone scale of strips from black to white, all broken into crude planes. Notice how the variation in tone is more dramatic in the lighter toned strips. The two left most strips are more finely facetted, approximating a curve in the left most one. In all strips, including the 5 tone scale, notice that the light area is substantially wider than the halftone area. This is the reason for the adage of "Compressing the Lights" in representing form - the work of turning the form is generally done by the separation of light from shadow and then the variation in the half tones and transition into shadow - rather than modelling in the lights or shadows, where it is very easy to overdo things and break up the form.
Diagram 6: Same object, light varies
There are three identical sets of coloured strips of medium chroma in these pictures, but the lighting varies between the pictures. The top set of strips is under a bluish light, the middle set is under white light (same amount of each wavelength), and the lower set is under a yellow orange light. In each set, the far left hand strip and the background surfaces are a mid tone neutral grey. This shows two main points: 1. Coloured lights reflect differently off different colours, for example the yellow orange light reflecting less strongly off the blue strip relative to the yellow strip, and 2. The consistency of the way different coloured surfaces reflect a particular light source creates a kind of ambience of that light source, while the local colours remain apparently the same - for example, the blue light set is an entirely different set of colours to the other two, but nonetheless looks like the same object.
Diagram 7: same skin toned objects, lights varies
There are three identical sets of coloured strips of in these pictures, but the lighting varies between the pictures. The top set of strips is under a bluish light, the middle set is under white light, and the lower set is under a yellow orange light. Once again, the far left hand strip in each set as well as the background surfaces are a mid tone neutral grey. The colours of the strips have been chosen to approximate some of the colours seen in light to medium toned human skin - Ruddy (dark reddish skin), cream, tanned (dark yellowish with high melanin), pale (bluish) and light pink. Notice how with these more neutral colours the half tones appear as the complementary hue to the colour of the light - for instance in the top bluish light, the halftones appear more orange, whereas in the bottom yellowish orange light, the half tones appear bluer or more purple.
Colour Painting from Still Life and Plaster Cast
These images are from a course covering:
Applying colour theory to observational painting
Organising colour and painting methodology
Colour gamuts - how to choose colours for your palette for a particular subject and aesthetic intention
Colour harmony, contrast and design
Below: Quick alla prima colour sketches in various colour gamuts done as class demos
Click the images to view and see the caption
A colour sketch using a limited palette of Cadmium Yellow, Permanent Alizarin Crimson, Ivory Black (as well as Titanium White). This combination, pushes the colour gamut into the yellow and orange side of the colour wheel, while limiting the strength of the relative blues. This suited the subject since the colour of the light was very orange. The challenge is to make the blues appear blue enough relative to the other colours - which means pushing all the other colours more orange.
The colour swatches in this study show the three relative primaries that were chosen (in that case Permanent Alizarin Crimson, Viridian and Yellow Ocre - a gamut that lacks a strong yellow or blue), the secondaries mixed from these and a tint of each. I find this number of colours and tints to be a good starting point as a set of mixing colours for free mixing (with a brush) the subtle colours that are observed in the actual painting. I would add to this a relative neutral mixed from all three of the relative primaries plus white. Note that the challenge with working within this gamut was capturing the sense of a the yellow orange light source, when it was not possible to mix a high chroma orange or blue. This can be tricky but automatically generates a colour harmony, so working with a limited palette like this can be a delightful way to manage the colour design.
As for Diagram 1, a the triad of colours chosen was cadmium yellow, permanent alizarin crimson and ivory black.
A Study by one of Scott's students, investigating colour in a monochromatic subject, where the features are divided into discrete planes