**-C**\ [[*section*/]\ *master_cpt*\ [**+h**\ [*hinge*]][**+u**\|\ **U**\ *unit*]\|\ *local.cpt*\|\ *color*\ :math:`_1`,\ *color*\ :math:`_2`\ [,\ *color*\ :math:`_3`\ ,...]]
    Name of an input CPT file or a comma-separated list of colors from which to build a CPT.
    If no argument is given then under modern mode we select the current CPT.
    Generally, the input can be many things:

    #. A standard GMT *master_cpt* file, e.g., *earth* 
       (see :ref:`Of Colors and Color Legends`) and can be either addressed
       by *master\_cpt* or *section*/*master_cpt* (without the **.cpt** extension).
    #. File name of already custom-made *local.cpt* file.
    #. Build a linear continuous CPT from *color*\ :math:`_1`,\ *color*\ :math:`_2`\ [,\ *color*\ :math:`_3`\ ,...]
       automatically, where *z* starts at 0 and is incremented by one for each color. In this case,
       *color*\ :math:`_i` can be a r/g/b (e.g., 255/100/75), or h-s-v triplet (e.g., 180-0.8-1),
       a c/m/y/k quadruple (e.g., 80/50/40/30), an HTML hexadecimal color (e.g. #aabbcc),
       or a :ref:`color name <RGBchart>`. No spaces between commas are allowed.

    A few modifiers pertains to hinges and units:

    - **+h** - If given a master CPT with soft hinges then you can enable the hinge at
      data value *hinge* [0], whereas for hard-hinge CPTs you can adjust the location
      of the hinge [0] but not disable it.
    - **+u** - For any other *master\_cpt*, you may convert their *z*-values from 
      another distance *unit* to meter.
    - **+U** - Likewise, you may convert their *z*-values from meter to another *unit*.

    **Note** - For **+u**\|\ **U**, a *unit* must be selected from **e**\|\ **f**\|\ **k**\|\ **M**\|\ **n**\|\ **u**.