After Ruby and gem install

 sturm@ansible-test  ~  colorls

 sturm@ansible-test  ~  gem which colorls
/home/sturm/.gem/ruby/2.5.0/gems/colorls-1.4.1/lib/colorls.rb

 sturm@ansible-test  ~  gem install colorls
ERROR:  While executing gem ... (Gem::FilePermissionError)
    You don't have write permissions for the /var/lib/gems/2.5.0 directory.

 sturm@ansible-test  ~ 