The API is fully documented in the tabs of the online FORD documentation.
And in the example directory, you will find these commented demos:
demo.f90 creates demo PPM files for each built-in colormap, plus a PPM file with the corresponding colorbars. It also demonstrates how to create your own colormap defined in an array and how to download a colormap from a .txt file.demo_reverse.f90 demonstrates the usage of the reverse=.true. option to reverse the direction of a colormap.colormaps_list.f90 generates the colormaps_list/COLORMAPS_LIST_*.md files.example1.f90 demonstrates how ForImage can be used to import/export PPM files.create.f90 demonstrates creating a custom colormap using methods like create_lagrange() and create_bezier().extract.f90 demonstrates how to create a specific colormap by extracting a specified number of colors of a colormap.info.f90 demonstrates how to obtain information about a colormap using the Colormaps_info class.modify.f90 demonstrates how you can modify a colormap with methods like shift(), in concrete cases.They can be launched with the command fpm run --example name_of_the_example (without the .f90 extension).
In the gtk-fortran-extra repository, you will also find a physical model demonstrating the use of ForColormap. It creates a movie with Turing patterns, displayed with various colormaps: