Orange is the only one
that has a half-intensity RGB component, therefore it shouldn't be included anyway.
It's only convention that the colours of the rainbow are thought of as they are, because of the way Isaac Newton's assistant described them back in the 16th century. One could just as well include "lime" since it is a continuum. It just happens that yellow is sufficiently different in perception from red to seem to warrant something in between.
( ,
Mon 17 Oct 2005, 21:43,
archived)
It's only convention that the colours of the rainbow are thought of as they are, because of the way Isaac Newton's assistant described them back in the 16th century. One could just as well include "lime" since it is a continuum. It just happens that yellow is sufficiently different in perception from red to seem to warrant something in between.