The Colour Wheel
The colour wheel is at the centre of colour theory and is a simple means of showing the relationships between colours. Usually, colours on the right side of the wheel are warm whereas those on the left are cool.
There are just three primary colours: red, yellow and blue. Primary colours cannot be made or mixed from other colours; they are the essentials from which all other colours are made.
The three primary colours
Mixing each of the primary colours with its neighbour in equal amounts produces the three secondary colours: green, orange and purple.
The secondary colours
Mixing a primary colour and a secondary colour (in a ratio of 2:1) produces a tertiary colour. These tertiary colours are usually given a two word name, such as blue-green, yellow-green, red-purple, blue-purple, red orange and yellow-orange.
The tertiary colours
Ratio means proportion; so a ratio of 2:1 means two measures of one colour and one measure of the other. For example: blue, blue and green gives blue-green, yellow, yellow and green gives yellow-green.
Colour Harmony
Harmony is simply a pleasing arrangement of parts. The parts may be music, poetry, ingredients in a recipe or colours.
Colour harmony produces something that is pleasing to the eye. It aims to interest the viewer and create a sense of balance and order in their visual experience. There are many theories of colour harmony and many formulae; the following two illustrations represent the most basic and safest of these.
Analagous colour schemes are based upon and three colours which are side by side on a 12 segment colour wheel and therefore harmonise with each other. For example: green yellow-green and yellow:
One of the three colours will usually predominate
Complementary colour schemes are based upon any two colours which are directly opposite each other on the colour wheel and threfore contrast with each other. For example: yellow-green and red-purple:
Opposing colours like these create the maximum contrast and maximum stability. Placing two complementarey colours next to each other will make them appear to increase in intensity; mixing them will produce a duller, less saturated colour.
Colour Theory
Colours have three aspects: hue, saturation and tone.
Hue refers to the "yellowness", "redness" or "blueness" of a colour. For example the difference between scarlet and crimson is one of hue, one of them having more yellowness than the other.
Saturation refers to the purity of a colour and is often used in the same way as intensity or brilliance. A really deep, rich colour is said to be highly saturated.
Tone refers to differences in the lightness or darkness of a hue. Tint is the usual term for a light hue or a colour to which white has been added. Shade is the usual term for a light hue or a colour to which black has been added.
Some colours are said to advance or come towards you and others are said to recede or go away from you. The advancing colours are usually warm (mainly red) whilst receding colours are usually cool (mainly blue). It is also worth noticing that saturated colours tend to advance whilst less saturated colours tend to recede.