How more “scrutable” is “color(0,4,0)” than “PS1”? There is no advantage to using either expression since both expressions are byzantine. How does the user know what values to the plugin for the numbers to achieve a particular color? The code snippet for changing the prompt color you provide is no more intuitive in marcel than in bash, fish, or zsh. How about if someone created a shell that could be scripted in plain English or any other human language.