The choice of colour for characters on your computer screen or video display terminal (VDT) is largely a matter of personal preference. However, several aspects of VDTs should be considered before you select the colours that you will use. The most important points to consider are the clarity (legibility) of the characters and the contrast between the colour of the characters and the background colour of the screen.
What should I know about "character colour"?
The consensus is that the "non-colours", white and black, and the colours yellow, green, and orange are generally most acceptable. The latter colours are in the middle of the visible spectrum (the range of colours that our eyes can detect) and are the easiest for the eye to see. Our eyes are not as receptive or sensitive to the colours at the extreme ends of the visible spectrum (e.g., blue, violet, and red). Characters in these colours should probably be avoided unless displayed on a light or contrasting background.
Occasionally colours may create "after images" following prolonged viewing. For example, after looking at a green image for a period when you look away white images may appear pink-tinged. This is a harmless, very short term effect that can be caused by any coloured source (e.g., a painted surface), not just VDTs.
What is display polarity?
Positive polarity means that a VDT or monitor displays dark characters on a light background, while negative polarity means that light characters are displayed on a dark background. One polarity has little advantage over the other. The resolution of positive polarity screens tends to be less affected by glare (screen reflections). Also, the dark characters on a light background is similar to what we are most used to in print materials. On the other hand, it tends to make screen flicker more noticeable. Given the same luminance (intensity of the light from the screen), negative polarity provides better character contrast and is less prone to flicker. User preference should be the determining factor when setting display polarity.
What should I know about image contrast and resolution?
Fairly sharp images and adequate contrast ratios of approximately 10:1 (image brightness to background) are typically required to make a display easier to read. What is acceptable to an individual will depend on character size, viewing distance and the type of task being done. A properly functioning monitor will typically provide adequate resolution. The exceptions may be early model or inexpensive colour computer monitors and TVs used as a display monitors.
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