Technology Tales

Adding visual appeal to bash command line scripts with colour variables on Linux

Published on 23^rd November 2025 Estimated Reading Time: 2 minutes

While I was updating some scripts to improve their functionality, I made some unexpected discoveries. One involved adding some colour to the output, and a second will come up later. The colours can be defined as values of variables, as you can see below:

# Colours
RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m' # no colour

In all cases, \033 is the shell escape sequence while [ is the control sequence initiator and m closes the sequence for colour definitions like we have here. A numeric value of 0 resets things to the default, which is how it is used in the no colour (NC) case that we have above to ensure that the colouration does not overflow beyond the intended text. Otherwise, 31 specifies red, 32 specifies green and 33 specifies yellow, giving options to use later on in the code. All of this is in line with the ANSI standard.

This is how these colour variables get used:

echo -e "\n${YELLOW}$(printf '*' {1..40}) All done $(printf '*' {1..40})${NC}\n"

The above is for an example with yellow text produced using ${YELLOW} segment after the newline sequence (\n)  that is activated b y the -e switch passed to the echo command. This is turned off by the ${NC} portion at the end of the text, again before a terminating newline sequence. One extra addition here is the part that outputs forty asterisks: $(printf '*' {1..40}). You could have $(printf '*%.0s' {1..40}) instead, which is clearer to some because of the null output character sequence %.0s. In the earlier example, I opted for the simpler option.