NO_COLOR Standard - Respecting User Color Preferences

The NO_COLOR Standard

The NO_COLOR environment variable is a widely adopted convention that signals CLI tools to suppress colored output. By checking for this variable, your tools respect user preferences and accessibility needs.

The Standard

From no-color.org:

Command-line software which outputs text with ANSI color added should check for the presence of a NO_COLOR environment variable that, when present (regardless of its value), prevents ANSI color. Checking for NO_COLOR= (empty string) is sufficient.

Implementation in Different Languages

Bash:

if [ -n "$NO_COLOR" ]; then
  RED=""
  GREEN=""
  RESET=""
else
  RED="\033[31m"
  GREEN="\033[32m"
  RESET="\033[0m"
fi

echo -e "${RED}Error message${RESET}"

Python:

import os, sys

USE_COLOR = (
    sys.stdout.isatty()
    and "NO_COLOR" not in os.environ
    and os.environ.get("TERM") != "dumb"
)

def colored(text, code):
    if USE_COLOR:
        return f"\033[{code}m{text}\033[0m"
    return text

Node.js:

const USE_COLOR = process.stdout.isTTY
  && !("NO_COLOR" in process.env)
  && process.env.TERM !== "dumb";

function colored(text, code) {
  return USE_COLOR
    ? `\x1b[${code}m${text}\x1b[0m`
    : text;
}

Go:

import "os"

func useColor() bool {
    _, noColor := os.LookupEnv("NO_COLOR")
    return !noColor && os.Getenv("TERM") != "dumb"
}

When to Disable Colors

Colors should be disabled when:

1. NO_COLOR environment variable is set
2. TERM is set to dumb
3. Output is not a terminal (piped or redirected)
4. The --no-color CLI flag is passed

FORCE_COLOR

Some tools also support FORCE_COLOR to enable colors even when output is piped:

# Force colors in piped output
FORCE_COLOR=1 my-tool | less -R

Accessibility Considerations

Some users disable colors because they use screen readers, have color vision deficiency, or use high-contrast terminal themes where ANSI colors reduce readability. Respecting NO_COLOR makes your tools more inclusive.