A rainbow has a continuous distribution of wavelengths. These are not at all the same thing as colors! Quoting Prof Brian Ripley <ripley at stats.ox.ac.uk>:
You would do well to get people to recognize more than a dozen spot colours, too -- we are tuned to recognizing quite large blobs of colour. We see only about a dozen colours in a rainbow, which has infinitely many and they are adjacent. -- Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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