Figure M.1 shows each of the 22 built-in color palettes,
stored in so-called cpt tables.
The programs makecpt and grd2cpt are used to access these master cpt tables
and translate/scale them to fit the user's range of -values.
The top half of the color bars in the Figure shows the original color scale, which can be either discrete or
continuous, though some (like globe) are a mix of the two.
The bottom half the color bar is an example of a discrete color scale build by using
makecpt -T-1/1/0.25.