.irbrc color coding Rails console by environment

.irbrc

# Add color coding based on Rails environment for safety

if defined? Rails
  banner = if Rails.env.production?
    "\e[41;97;1m #{Rails.env} \e[0m "
  else
    "\e[42;97;1m #{Rails.env} \e[0m "
  end

  # Build a custom prompt
  IRB.conf[:PROMPT][:CUSTOM] = IRB.conf[:PROMPT][:DEFAULT].merge(
    PROMPT_I: banner + IRB.conf[:PROMPT][:DEFAULT][:PROMPT_I],
  )

  # Use custom prompt by default
  IRB.conf[:PROMPT_MODE] = :CUSTOM
end

Relevant "docs" for customizing the IRB prompt: https://github.com/ruby/irb/blob/master/lib/irb.rb#L144-L233