• Colour detection is effective when images are in front (important for large or multiscreen interfaces).
  
  
• Blue is useful as a background as the eye is most sensitive to this colour on the peripheries.
  
  
• Reds and yellows (warm) come toward the viewer whilst cold colours go away. This may underline levels of activity.
  
  
• Contrast can make the same shape appear lighter or darker.
  
  
• Avoid confusing effects, i.e. clashes, given that colour is interpreted by the brain, and optical illusions may ensue.
  
  
• Bright screens may lead to flicker, and in turn annoyance, headaches and discomfort grows.
  
  
• Simply avoid inconsistent, garish use and unnecessary changes.
  
  
• Use of a logo may reduce available colours for the rest of the screen.
  
  
• Individual preferences exist, therefore resetting colour usage parameters should be possible. For example, changing a character's clothes as in "Super Street Fighter II".
  
  

Different colours give very different messages to readers. Even if the analogy of the red rag to a bull is a fallacy, out of scheme colours and flashing inks will distract the user. The use of these should be minimal otherwise their impact will be entirely lost, and the first consideration will be violated!