Understanding the Colour Wheel: Primary, Secondary and Complementary Colours

Ask a class of Grade 6 students to paint a sunset and most of them will reach straight for orange. Ask them why the orange looks flat next to the blue sky they painted first, and the room goes quiet. That gap - between using a colour and understanding it - is what the colour wheel closes.

The colour wheel is not decoration for the front of an exercise book. It is a working tool. Once you can see where a colour sits on the wheel, you can predict what will happen when you put it next to another one, and you stop mixing by accident.

The three primary colours

Red, yellow and blue are called primary because no amount of mixing will produce them. Every other colour on the wheel is descended from these three. In the Sri Lankan syllabus you meet them in Grade 6, and you keep returning to them right up to Advanced Level.

Set them at equal distances around a circle - red at the top, yellow at the lower right, blue at the lower left. That triangle is the skeleton of the whole wheel, and everything else fills in between the three points.

Secondary and tertiary colours

Mix two primaries in equal amounts and you get a secondary colour. Red and yellow give orange, yellow and blue give green, blue and red give violet. Place each secondary between the two primaries that made it, and the wheel now has six colours.

Keep going and you get tertiary colours - red-orange, yellow-orange, yellow-green, blue-green, blue-violet and red-violet - made by mixing a primary with the secondary beside it. A twelve-colour wheel is enough for any school-level painting.

The important habit is to mix these yourself rather than buying them ready-made. A green you mixed from your own yellow and blue will sit naturally beside the other colours in your painting, because it shares their pigment. A tube green often will not.

Warm and cool: the two halves of the wheel

Draw a line through the wheel and you split it in two. Reds, oranges and yellows are the warm half; greens, blues and violets are the cool half. This is the single most useful thing the wheel tells you, because warm colours appear to come forward and cool colours appear to recede.

That is why a distant hill painted in cool blue-grey sits behind a foreground painted in warm browns, even though both are flat on the same sheet of paper. You are not drawing depth - you are colouring it.

Complementary colours and why they matter

Colours directly opposite each other on the wheel are complementary: red and green, blue and orange, yellow and violet. Put a pair side by side and each looks more intense than it does alone. Put a small area of one inside a large area of the other and the small area becomes the focal point of the picture.

Complementaries also do the opposite job. Mix a little of a colour's complement into it and the colour turns duller and greyer - which is exactly how you make a shadow that still belongs to the object. A shadow on a red pot is not black; it is red with a touch of green in it.

This one idea will improve a still life faster than any other. Students who paint shadows in grey or black end up with objects that look pasted onto the paper. Students who mix shadows from complements end up with objects that sit on the table.

Putting it to work

Before you start a painting, decide which half of the wheel will dominate. A picture that uses mostly warm colours with a few cool accents will hold together. A picture that uses every colour equally usually will not.

Then pick one complementary pair to carry the focal point, and keep the rest of the palette close together on the wheel. This is the discipline behind most of the sample artworks on this site - look at the vessel and pattern designs and you will see the same restraint at work.

• Mix your own secondaries instead of using tube colours straight.
• Decide on a warm or cool bias before the first brushstroke.
• Build shadows from a colour's complement, never from black.
• Save the strongest complementary contrast for the focal point.