Can I define a short command, say dark, that is equivalent to, say
set recolor-lightcolor \#002b36
set recolor-darkcolor \#839496
?
You can try to go for a key bind instead of command.
In case you want both commands available within a single combination then put to config ~/.config/zathura/zathurarc file something like:
map <C-l> feedkeys ":set recolor-lightcolor \#002b36<Return>:set recolor-darkcolor \#839496<Return>"
PS. Not sure why you need this, but if you also can just save it by default in the same config file so it will be loaded every time you launch zathura without additional moves. Just add your lines to the config file mentioned above.
PS. More detailed information about config file you can find at official documentation page