Open from Samples
If you do not have any available CPT files, or you would like to examine or experiment with some ready-made CPT files, some have been provided: these are the standard CPT files included in an installation of that excellent program-suite 'GMT - The Generic Mapping Tools': a free, open source software that is widely used across the Earth, Ocean, and Planetary sciences. You can download it from their website: https://www.generic-mapping-tools.org/download/ (Link will open in your Browser).
To open one of these sample CPT Files, click 'File > Open from Samples', and choose the file that you wish to use.