For example, a dog may literally see red (that is, what humans would call red) when looking at Garfield the cat, who seems orange to normal humans and who often looks yellow to deuteranopes
1) Protanopes and deuteranopes
are able to match all red-green mixture ratios.
Protanopes have a normal M gene, whereas deuteranopes
have a normal L gene.
Those with colour vision defects see the spot differently; for example protanopes usually describe it as blue or dark because their red sensitivity is reduced, and most deuteranopes
cannot see the spot at all.
Hidden digit plates seem to work better for deuteranopes than other colour deficient individuals but they have an overall sensitivity of only around 50%.
The classification plates are more effective for deuteranopes than protanopes, with a correct classification possible for around 90% of deuteranopes and around 80% of protanopes.
22) All deuteranopes and 96% of protanopes failed the test.
The neutral points for deuteranopes
, protanopes and tritanopes are around 498nm, 492nm and 569nm respectively.
Table 1 Examples of colours that might be confused by colour deficient observers Colour deficiency Examples of colours that might be confused Protanope Blue--green/white/red Pale blue/purple/magenta Red/orange/yellow/green Deuteranope
Purple/Grey/greenish blue-green Red/orange/yellow/green Red/brown, green/brown Tritanope Yellow/white Violet/yellow-green Red/red-purple