dmenu:tldr:4a007

This command is a combination of multiple commands and pipes.

• echo is a command used to display text or variables in the terminal.
• -e flag is used to enable the interpretation of backslash escapes in the echo command.
• ${red}, ${green}, and ${blue} are variables or placeholders that are expected to be defined with color codes or text before executing the command.
• | is a pipe symbol used to pass the output of one command as the input of another command.
• dmenu is a dynamic menu for X, a command-line tool that provides a graphical menu for selecting options or displaying information.

So, the command sends the newline-separated values of ${red}, ${green}, and ${blue} as input to dmenu. The expected outcome is to display these values in a dmenu popup window, possibly to choose a color or perform some action based on the selected value.