**-C**\ [*cpt*\|\ *master*\ [**+h**\ [*hinge*]][**+i**\ *zinc*][**+u**\|\ **U**\ *unit*] \|\ *color1,color2*\ [,\ *color3*\ ,...]]
    Name of a CPT file. Alternatively, supply the name of a GMT color master
    dynamic CPT [*turbo*, but we use *geo* for @earth_relief and *srtm* for @srtm_relief data] to
    automatically determine a continuous CPT from the grid's *z*-range; you may round the range
    to the nearest multiple of *zinc* by adding **+i**\ *zinc*. If given a GMT Master soft-hinge CPT
    (see :ref:`Of Colors and Color Legends`) then you can enable the hinge at data value *hinge* [0] via **+h**,
    whereas for hard-hinge CPTs you can adjust the location of the hinge [0].
    For other CPTs, you may convert their *z*-values from meter to another distance unit (append **+U**\ *unit*)
    or from another unit to meter (append **+u**\ *unit*), with *unit* taken from
    **e**\|\ **f**\|\ **k**\|\ **M**\|\ **n**\|\ **u**.
    Yet another option is to specify **-C**\ *color1*\ ,\ *color2*\ [,\ *color3*\ ,...]
    to build a linear continuous CPT from those colors automatically.
    In this case *color*\ **n** can be a r/g/b triplet, a color name,
    or an HTML hexadecimal color (e.g. #aabbcc).  If no argument is given to **-C**
    then under modern mode we select the current CPT.
