Colour theory is a small set of ideas that help you mix the colour you want and choose colours that look good together. You don't need to memorise charts. A few basics will change how you paint.
The colour wheel
Start with the three primaries: red, yellow and blue. Mix two of them and you get the secondaries: orange, green and purple. Mix a primary with its neighbouring secondary and you get the in-between tertiaries, like yellow-green or red-purple.
Hue, value and saturation
- Hue is the colour family: red, blue, green.
- Value is how light or dark it is.
- Saturation is how strong or muted it is.
Value matters most. A painting with clear lights and darks reads well even in black and white. Squint at your work: if everything blurs into one middle tone, push your darks darker.
Warm and cool
Warm colours (reds, oranges, yellows) seem to come forward. Cool colours (blues, greens, purples) seem to sit back. Each primary also has a warm and a cool version, so a palette with two of each mixes cleaner, brighter colours.
Complementary colours
Colours opposite each other on the wheel, like orange and blue, make each other look brighter when placed side by side. Mixed together, they calm each other down into rich greys and browns, which are far more alive than shadows made with black.
Try this: paint a 12-step colour wheel using only the paints you own. You'll learn more about your own tubes in one afternoon than from any printed chart.