colormap variable as a function of another variable

I need to have a matching vector to define the colours, with one colour for each point, that value going from -6 to +10, but defined as cm(c) where c goes from 1 to 16, with 1 corresponding to -6 and 16 corresponding to 10.

cm is defined as:

cm = flipud(colormap(jet(16)));

[Walter Roberson]

-6 to +10 is 17 values, which you want to map to 16 colors. Which two values should both be mapped to the same color?