There are 2 ways of using this theme. The first is to replace the existing colorname array and default* functions with the content in the header file.
The second is to remove the colorname array and default* functions in your config.h and replace it with:
#include "challenger-deep-theme.h"
If you go for the second option, you must of course have the header file in the same directory as the config.h.
Afterwards, recompile st with sudo make install and you're done!
❤️ Thanks to JanSHoekstra for porting this theme.