Know the feeling? In the morning, you painted a wall in the hall a rich tomato red – and in the evening you switch on the lights and it looks more like the magenta you definitely did not want. The reason is that the lamp you chose does not render colours as well as it should.

While daylight contains all the colours visible to the human eye, lamps have differing colour rendering characteristics. These are indicated by the colour rendering index Ra: the higher it is, the better colours are rendered. The best possible index is Ra 100, which means that all colours are rendered naturally. The colour rendering indices of lamps range from Ra 20 to 100. As a general rule, incandescent lamps and halogen lamps render all colours very well; high-quality energy-saving and fluorescent lamps reach Ra values of 80 to 90.

Light colours: from warm to cool

The light colour of a lamp is another important factor to consider when it comes to ensuring successful interaction between light and colour. Light colour affects our mood. It indicates the colour appearance of a lamp's light and is expressed as a colour temperature in degrees Kelvin (K). As a general rule:

• warm light colours (up to around 2,900 K) have a soothing effect and lend themselves very well to cosy domestic situations,
• cool light colours with a greater blue component (over 3,300 K) have an energizing  effect and are recommended wherever concentration and deliberation are required.
  
  

Halogen lamp light imitates the characteristics of natural daylight the best. Incandescent lamps emit a warm-white light with a hint of orange-yellow; energy-saving and fluorescent lamps are available today in colours ranging from "extra warm white" (2,700 K) to "daylight white" (approx. 6,000 K). Back to that newly painted wall: by selecting the right lamp, you can enhance the required colour/light effect.