Colour temperature does have something to do with it.
Our wind-free test tunnel at Shebbear is made from blue plastic barrels spigoted end to end. The light on any target suspended in the tunnel is therefore mainly blue; the pigmented plastic filters out the longer wavelengths. Now, the tube's maximum length is 42 yards, but no matter how I try, I cannot make any of my scopes tell me the card is 42 yards away, they all tell me it's only 40 yards. A tape measure soon proves them all wrong.