Implications from the physiology of the eye
 

• Do not use blue for small objects (since human sensitivity for blue is very low, particularly in the fovea)
• Blue is a good background color (since human sensitivity for blue is very low and since receptors for blue are roughly evenly distributed over the retina)
• Neighboring objects should not merely differ by their amount of blue.
  • a a a (red, red with 50% blue, red with 100% blue)
  • a a a (red, red with 50% green, red with 100% green)
• If red and green are used for small objects, these should be in the center (since the sensitivity for these colors is far higher in the center).
• If red and green are used as signals (warnings) in the periphery, they should have additional emphasis (like blinking or change in size).  
• Black, white, yellow and blue can be used in the periphery since the sensitivity of the retina is roughly the same.