- Build a 12-part colour wheel and sort colours into groups
- Find complementary, analogous and triadic schemes on the wheel
- Read a hex code (#RRGGBB) and describe it in words
Why is red so common on road signs, while green or blue is common on hospital signs? Why can an orange life jacket be seen from far away against a blue sea? The answer lies in colour theory — the knowledge of how colours relate to one another and how they affect people.
The colour wheel
In 1704 Isaac Newton arranged the colours of the spectrum in a circle in his book Opticks. The traditional colour wheel that painters use is built on three primary colours: red, yellow and blue. They cannot be made by mixing other paints. Mixing two primaries gives a secondary colour, and mixing a primary with a neighbouring secondary gives a tertiary colour. The result is a 12-part wheel.
| Group | Colours | How they are made |
|---|---|---|
| Primary (3) | red, yellow, blue | cannot be mixed from other colours |
| Secondary (3) | orange, green, violet | red + yellow = orange; yellow + blue = green; blue + red = violet |
| Tertiary (6) | red-orange, yellow-orange, yellow-green, blue-green, blue-violet, red-violet | a primary + the neighbouring secondary |
Every colour has three properties: hue (red, blue and so on), value (how light or dark it is) and saturation (how bright or dull it is). Adding white makes a tint, adding black makes a shade, and adding grey makes a tone with lower saturation.
Warm and cool colours
One half of the wheel holds the warm colours — red, orange, yellow: they are linked with fire, sun and energy and seem to come towards the viewer. The other half holds the cool colours — green, blue, violet: they are linked with water, sky and calm and seem to move away. That is why distant mountains in a landscape are painted bluish.
Colour harmony
Colours that sit directly opposite each other on the wheel are complementary colours: red — green, yellow — violet, blue — orange. Placed side by side they make each other look brighter; mixed together they “cancel out” into a grey-brown. Harmony schemes help you choose colours by their positions on the wheel.
| Scheme | How to find it on the wheel | Effect |
|---|---|---|
| Monochromatic | light and dark versions of one hue | calm, unified |
| Analogous | 3 colours side by side on the wheel | soft, natural |
| Complementary | 2 colours directly opposite | strong, eye-catching |
| Split-complementary | one colour + the two neighbours of its complement | contrasting but gentler |
| Triadic | 3 colours evenly spaced around the wheel | lively, playful, balanced |
Leyla is designing a poster for a school concert. The main colour is blue. Find the complementary, analogous, split-complementary and triadic schemes for her.
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2) Analogous: blue-green, blue, blue-violet.
3) Split-complementary: blue + the neighbours of orange — yellow-orange and red-orange.
4) Triadic (every 4 “hours”): blue, red, yellow.
A concert poster must catch the eye, so the complementary scheme is the best choice: orange lettering on a blue background can be read from far away.
Writing colour as numbers: hex codes
A computer writes a colour as amounts of red, green and blue light: #RRGGBB. Each pair is a hexadecimal number from 00 (none) to FF (255, the maximum). For example, #FF0000 means full red light with no green and no blue. Whenever the three pairs are equal, the colour is white, black or a grey.
| Hex | Colour | Described in words |
|---|---|---|
| #FF0000 | red | full red, no green or blue; the bright red of a fire engine |
| #FFFF00 | yellow | full red + full green light; a bright lemon yellow |
| #0000FF | blue | blue light only; a deep, saturated blue |
| #FF8000 | orange | full red + half green; the colour of an orange |
| #008000 | green | half green only; a medium leaf green |
| #800080 | purple | half red + half blue; a dark purple |
| #808080 | grey | all three pairs equal (80) — a medium grey |
| #FFFFFF | white | all three lights at maximum |
Key points
- The painter's colour wheel has 3 primary, 3 secondary and 6 tertiary colours.
- Warm colours come forward; cool colours recede.
- Complementary colours are opposite; a primary's complement is the mix of the other two primaries.
- Harmony schemes: monochromatic, analogous, complementary, split-complementary, triadic.
- Paints get darker when mixed, lights (RGB) get lighter when added; a hex code is written #RRGGBB.
Check yourself
10 questions. Every correct answer earns XP.